Tunable rf filter paths for tunable rf filter structures

ABSTRACT

This disclosure relates generally to radio frequency (RF) filter structures. In one embodiment, an RF filter structure includes a first resonator and a second resonator. The second resonator is operably associated with the first resonator such that an energy transfer factor between the first resonator and the second resonator is less than 10%. The first resonator includes a first inductor and a first capacitive structure electrically connected to the first inductor, while the second resonator has a second inductor and a second capacitive structure electrically connected to the second inductor. A displacement between the first inductor and the second inductor is less than or equal to half a maximum lateral width of the second inductor. To set an electric coupling coefficient, a first cross-coupling capacitive structure is electrically connected between the first resonator and the second resonator.

RELATED APPLICATIONS

The present application claims priority to U.S. Provisional PatentApplication No. 61/831,666, filed Jun. 6, 2013; U.S. Provisional PatentApplication No. 61/860,932, filed Aug. 1, 2013; U.S. Provisional PatentApplication No. 61/909,028, filed Nov. 26, 2013; U.S. Provisional PatentApplication No. 61/938,884, filed Feb. 12, 2014; U.S. Provisional PatentApplication No. 61/949,581, filed Mar. 7, 2014; U.S. Provisional PatentApplication No. 61/951,844, filed Mar. 12, 2014; U.S. Provisional PatentApplication No. 61/982,946, filed Apr. 23, 2014; U.S. Provisional PatentApplication No. 61/982,952, filed Apr. 23, 2014; U.S. Provisional PatentApplication No. 61/982,971, filed Apr. 23, 2014; and U.S. ProvisionalPatent Application No. 62/008,192, filed Jun. 5, 2014.

The present application is related to concurrently filed U.S. patentapplication Ser. No. ______, entitled “TUNABLE RF FILTER STRUCTUREFORMED BY A MATRIX OF WEAKLY COUPLED RESONATORS;” concurrently filedU.S. patent application Ser. No. ______, entitled “HIGH QUALITY FACTORINTERCONNECT FOR RF CIRCUITS;” concurrently filed U.S. patentapplication Ser. No. ______, entitled “NONLINEAR CAPACITANCELINEARIZATION;” concurrently filed U.S. patent application Ser. No.______, entitled “TUNABLE RF FILTER BASED RF COMMUNICATIONS SYSTEM;” andconcurrently filed U.S. patent application Ser. No. ______, entitled“MULTI-BAND INTERFERENCE OPTIMIZATION.”

All of the applications listed above are hereby incorporated herein byreference in their entireties.

FIELD OF THE DISCLOSURE

Embodiments of the present disclosure relate to radio frequency (RF)communications systems, which may include RF front-end circuitry, RFtransceiver circuitry, RF amplifiers, direct current (DC)-DC converters,RF filters, RF antennas, RF switches, RF combiners, RF splitters, thelike, or any combination thereof.

BACKGROUND

As wireless communications technologies evolve, wireless communicationssystems become increasingly sophisticated. As such, wirelesscommunications protocols continue to expand and change to take advantageof the technological evolution. As a result, to maximize flexibility,many wireless communications devices must be capable of supporting anynumber of wireless communications protocols, each of which may havecertain performance requirements, such as specific out-of-band emissionsrequirements, linearity requirements, or the like. Further, portablewireless communications devices are typically battery powered and needto be relatively small, and have low cost. As such, to minimize size,cost, and power consumption, RF circuitry in such a device needs to beas simple, small, flexible, and efficient as is practical. Thus, thereis a need for RF circuitry in a communications device that is low cost,small, simple, flexible, and efficient.

SUMMARY

This disclosure relates generally to radio frequency (RF) filterstructures. In one embodiment, an RF filter structure is provided thatincludes a first resonator and a second resonator. The first resonatorand the second resonator are weakly coupled to one another. In thisembodiment, the second resonator is operably associated with the firstresonator such that an energy transfer factor between the firstresonator and the second resonator is less than 10%. The first resonatorincludes a first inductor and a first capacitive structure electricallyconnected to the first inductor, while the second resonator has a secondinductor and a second capacitive structure electrically connected to thesecond inductor. The second inductor of the second resonator has amaximum lateral width. A displacement between the first inductor and thesecond inductor is less than or equal to half the maximum lateral widthof the second inductor. Thus, the first inductor and the second inductorare in relatively close proximity. In order to set an electric couplingcoefficient between the first resonator and the second resonator, afirst cross-coupling capacitive structure is electrically connectedbetween the first resonator and the second resonator.

Those skilled in the art will appreciate the scope of the presentdisclosure and realize additional aspects thereof after reading thefollowing detailed description of the preferred embodiments inassociation with the accompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings incorporated in and forming a part of thisspecification illustrate several aspects of the disclosure, and togetherwith the description serve to explain the principles of the disclosure.

FIG. 1 shows traditional communications circuitry according to the priorart.

FIG. 2 shows the traditional communications circuitry according to theprior art.

FIG. 3 shows the traditional communications circuitry according to theprior art.

FIG. 4 shows RF communications circuitry according to one embodiment ofthe RF communications circuitry.

FIG. 5 is a graph illustrating filtering characteristics of a firsttunable RF filter path and a second tunable RF filter path illustratedin FIG. 4 according to one embodiment of the first tunable RF filterpath and the second tunable RF filter path.

FIGS. 6A and 6B are graphs illustrating filtering characteristics of thefirst tunable RF filter path and the second tunable RF filter path,respectively, illustrated in FIG. 4 according to an alternate embodimentof the first tunable RF filter path and the second tunable RF filterpath, respectively.

FIG. 7 shows the RF communications circuitry according to one embodimentof the RF communications circuitry.

FIG. 8 shows the RF communications circuitry according to an alternateembodiment of the RF communications circuitry.

FIGS. 9A and 9B are graphs illustrating filtering characteristics of thefirst tunable RF filter path and the second tunable RF filter path,respectively, illustrated in FIG. 8 according to an additionalembodiment of the first tunable RF filter path and the second tunable RFfilter path.

FIGS. 10A and 10B are graphs illustrating filtering characteristics of afirst traditional RF duplexer and a second traditional RF duplexer,respectively, illustrated in FIG. 3 according to the prior art.

FIG. 11 shows the RF communications circuitry according to oneembodiment of the RF communications circuitry.

FIG. 12 shows the RF communications circuitry according to an alternateembodiment of the RF communications circuitry.

FIG. 13 shows the RF communications circuitry according to an additionalembodiment of the RF communications circuitry.

FIG. 14 shows the RF communications circuitry according to anotherembodiment of the RF communications circuitry.

FIG. 15 shows the RF communications circuitry according to a furtherembodiment of the RF communications circuitry.

FIG. 16 shows the RF communications circuitry according to oneembodiment of the RF communications circuitry.

FIG. 17 shows the RF communications circuitry according to an alternateembodiment of the RF communications circuitry.

FIG. 18 shows the RF communications circuitry according to an additionalembodiment of the RF communications circuitry.

FIG. 19 shows the RF communications circuitry according to anotherembodiment of the RF communications circuitry.

FIG. 20 shows the RF communications circuitry according to a furtherembodiment of the RF communications circuitry.

FIG. 21 illustrates one embodiment of a tunable radio frequency (RF)filter structure that defines multiple tunable RF filtering paths thatare independent of each other.

FIG. 22 illustrates one embodiment of a tunable RF filter path shown inFIG. 21 having cross-coupling capacitors arranged in a V-bridgestructure.

FIG. 23 illustrates another embodiment of the tunable RF filter pathshown in FIG. 21 having cross-coupling capacitors arranged in anX-bridge structure.

FIG. 24 illustrates another embodiment of the tunable RF filter pathshown in FIG. 21 having a cross-coupling capacitor arranged in a singlepositive bridge structure.

FIG. 25 illustrates another embodiment of the tunable RF filter pathshown in FIG. 21 having cross-coupling capacitors arranged in anH-bridge structure.

FIG. 26 illustrates another embodiment of the tunable RF filter pathshown in FIG. 21 having cross-coupling capacitors arranged in a doubleH-bridge structure.

FIG. 27 illustrates another embodiment of the tunable RF filter pathshown in FIG. 21 having four weakly coupled resonators with magnetic andelectric couplings between them.

FIGS. 28A-28D disclose different embodiments of a tunable RF filterstructure, each with a different number of input terminals and outputterminals.

FIG. 29 illustrates one embodiment of a tunable radio frequency (RF)filter structure having four resonators and cross-coupling capacitivestructures electrically connected between the four resonators so as toform a 2×2 matrix with the four resonators. In alternative embodiments,fewer (e.g., three) resonators or more (e.g., five or more) resonatorsmay be provided.

FIG. 30 illustrates another embodiment of a tunable RF filter structurehaving M number of rows and N number of columns of resonators that areelectrically connected by cross-coupling capacitive structures so thatthe tunable RF filter structure is arranged so as to form an M×Ntwo-dimensional matrix of the resonators.

FIG. 31 illustrates the tunable RF filter structure shown in FIG. 30electrically connected to various RF antennas.

FIG. 32 illustrates the tunable RF filter structure shown in FIG. 30with two tunable RF filter paths highlighted for performing MultipleInput Multiple Output (MIMO), Single Input Multiple Output (SIMO),Multiple Input Single Output (MISO), and Single Input Single Output(SISO) operations.

FIG. 33 illustrates another embodiment of a tunable RF filter structurewith amplifier stages electrically connected within and between tunableRF filter paths.

FIG. 34 illustrates an embodiment of a tunable RF filter structureintegrated into an integrated circuit (IC) package with multiple andseparate semiconductor dies.

FIG. 35 illustrates an embodiment of the same tunable RF filterstructure shown in FIG. 34, but now integrated into an IC package with asingle semiconductor die.

FIG. 36 illustrates one embodiment of a tunable RF filter structurehaving resonators and cross-coupling capacitive structures electricallyconnected between the resonators so as to form a three-dimensionalmatrix of the resonators.

DETAILED DESCRIPTION

The embodiments set forth below represent the necessary information toenable those skilled in the art to practice the disclosure andillustrate the best mode of practicing the disclosure. Upon reading thefollowing description in light of the accompanying drawings, thoseskilled in the art will understand the concepts of the disclosure andwill recognize applications of these concepts not particularly addressedherein. It should be understood that these concepts and applicationsfall within the scope of the disclosure and the accompanying claims.

RF communications circuitry, which includes a first RF filter structure,is disclosed according to a first embodiment of the present disclosure.The first RF filter structure includes a first tunable RF filter pathand a second tunable RF filter path. The first tunable RF filter pathincludes a pair of weakly coupled resonators. Additionally, a firstfilter parameter of the first tunable RF filter path is tuned based on afirst filter control signal. A first filter parameter of the secondtunable RF filter path is tuned based on a second filter control signal.

In one embodiment of the first RF filter structure, the first tunable RFfilter path is directly coupled between a first common connection nodeand a first connection node. The second tunable RF filter path isdirectly coupled between a second connection node and the first commonconnection node.

In one embodiment of the RF communications system, the first tunable RFfilter path and the second tunable RF filter path do not significantlyload one another at frequencies of interest. As such, by directlycoupling the first tunable RF filter path and the second tunable RFfilter path to the first common connection node; front-end RF switchingelements may be avoided, thereby reducing cost, size, and non-linearity;and increasing efficiency and flexibility of the RF communicationssystem. In one embodiment of the RF communications system, the firstcommon connection node is coupled to an antenna.

Embodiments of the RF communications system include frequency divisionduplex (FDD) applications, time division duplex (TDD) applications,carrier-aggregation (CA) applications, multiple antenna applications,MIMO applications, hybrid applications, applications supporting multiplecommunications bands, the like, or any combination thereof.

FIG. 1 shows traditional communications circuitry 10 according to theprior art. The traditional communications circuitry 10 illustrated inFIG. 1 is a time-division duplex (TDD) system, which is capable oftransmitting and receiving RF signals, but not simultaneously. Such asystem may also be called a half-duplex system. Additionally, thetraditional communications circuitry 10 may be used as a simplex system,which is a system that only transmits RF signals or only receives RFsignals. Traditional communications systems often use fixed frequencyfilters. As a result, to cover multiple communications bands, switchingelements are needed to select between different signal paths.

The traditional communications circuitry 10 includes traditional RFsystem control circuitry 12, traditional RF front-end circuitry 14, anda first RF antenna 16. The traditional RF front-end circuitry 14includes traditional RF front-end control circuitry 18, firsttraditional antenna matching circuitry 20, first traditional RF receivecircuitry 22, first traditional RF transmit circuitry 24, a firsttraditional RF switch 26, and a second traditional RF switch 28. Thefirst traditional RF switch 26 is coupled between the first traditionalantenna matching circuitry 20 and the first traditional RF receivecircuitry 22. The second traditional RF switch 28 is coupled between thefirst traditional antenna matching circuitry 20 and the firsttraditional RF transmit circuitry 24. The first RF antenna 16 is coupledto the first traditional antenna matching circuitry 20. The firsttraditional antenna matching circuitry 20 provides at least partialimpedance matching between the first RF antenna 16 and either the firsttraditional RF receive circuitry 22 or the first traditional RF transmitcircuitry 24.

The traditional RF system control circuitry 12 provides the necessarycontrol functions needed to facilitate RF communications between thetraditional communications circuitry 10 and other RF devices. Thetraditional RF system control circuitry 12 processes baseband signalsneeded for the RF communications. As such, the traditional RF systemcontrol circuitry 12 provides a first traditional upstream transmitsignal TUT1 to the first traditional RF transmit circuitry 24. The firsttraditional upstream transmit signal TUT1 may be a baseband transmitsignal, an intermediate frequency (IF) transmit signal, or an RFtransmit signal. Conversely, the traditional RF system control circuitry12 receives a first traditional downstream receive signal TDR1 from thefirst traditional RF receive circuitry 22. The first traditionaldownstream receive signal TDR1 may be a baseband receive signal, an IFreceive signal, or an RF receive signal.

The first traditional RF transmit circuitry 24 may include up-conversioncircuitry, amplification circuitry, power supply circuitry, filteringcircuitry, switching circuitry, combining circuitry, splittingcircuitry, dividing circuitry, clocking circuitry, the like, or anycombination thereof. Similarly, the first traditional RF receivecircuitry 22 may include down-conversion circuitry, amplificationcircuitry, power supply circuitry, filtering circuitry, switchingcircuitry, combining circuitry, splitting circuitry, dividing circuitry,clocking circuitry, the like, or any combination thereof.

The traditional RF system control circuitry 12 provides a traditionalfront-end control signal TFEC to the traditional RF front-end controlcircuitry 18. The traditional RF front-end control circuitry 18 providesa first traditional switch control signal TCS1 and a second traditionalswitch control signal TCS2 to the first traditional RF switch 26 and thesecond traditional RF switch 28, respectively, based on the traditionalfront-end control signal TFEC. As such, the traditional RF systemcontrol circuitry 12 controls the first traditional RF switch 26 and thesecond traditional RF switch 28 via the traditional front-end controlsignal TFEC. The first traditional RF switch 26 is in one of an ON stateand an OFF state based on the first traditional switch control signalTCS1. The second traditional RF switch 28 is in one of an ON state andan OFF state based on the second traditional switch control signal TCS2.

Half-duplex operation of the traditional communications circuitry 10 isaccomplished using the first traditional RF switch 26 and the secondtraditional RF switch 28. When the traditional communications circuitry10 is transmitting RF signals via the first RF antenna 16, the firsttraditional RF switch 26 is in the OFF state and the second traditionalRF switch 28 is in the ON state. As such, the first traditional antennamatching circuitry 20 is electrically isolated from the firsttraditional RF receive circuitry 22 and the first traditional antennamatching circuitry 20 is electrically coupled to the first traditionalRF transmit circuitry 24. In this regard, the traditional RF systemcontrol circuitry 12 provides the first traditional upstream transmitsignal TUT1 to the first traditional RF transmit circuitry 24, whichprovides a traditional transmit signal TTX to the first RF antenna 16via the second traditional RF switch 28 and the first traditionalantenna matching circuitry 20 based on the first traditional upstreamtransmit signal TUT1.

When the traditional communications circuitry 10 is receiving RF signalsvia the first RF antenna 16, the first traditional RF switch 26 is inthe ON state and the second traditional RF switch 28 is in the OFFstate. As such, the first traditional antenna matching circuitry 20 isisolated from the first traditional RF transmit circuitry 24 and thefirst traditional antenna matching circuitry 20 is electrically coupledto the first traditional RF receive circuitry 22. In this regard, thefirst traditional antenna matching circuitry 20 receives the RF signalsfrom the first RF antenna 16 and forwards the RF signals via the firsttraditional RF switch 26 to the first traditional RF receive circuitry22. The first traditional RF switch 26 provides a traditional receivesignal TRX to the first traditional RF receive circuitry 22, whichprovides a first traditional downstream receive signal TDR1 to thetraditional RF system control circuitry 12 based on the traditionalreceive signal TRX.

Since the traditional communications circuitry 10 illustrated in FIG. 1is a half-duplex system, during operation, the first traditional RFswitch 26 and the second traditional RF switch 28 are not simultaneouslyin the ON state. Therefore, the first traditional RF receive circuitry22 and the first traditional RF transmit circuitry 24 are isolated fromone another. As such, the first traditional RF receive circuitry 22 andthe first traditional RF transmit circuitry 24 are prevented frominterfering with one another.

FIG. 2 shows the traditional communications circuitry 10 according tothe prior art. The traditional communications circuitry 10 illustratedin FIG. 2 is similar to the traditional communications circuitry 10illustrated in FIG. 1, except in the traditional communicationscircuitry 10 illustrated in FIG. 2, the traditional RF front-end controlcircuitry 18, the first traditional RF switch 26, and the secondtraditional RF switch 28 are omitted, and the traditional RF front-endcircuitry 14 further includes a first traditional RF duplexer 30. Thefirst traditional RF duplexer 30 is coupled between the firsttraditional antenna matching circuitry 20 and the first traditional RFreceive circuitry 22, and is further coupled between the firsttraditional antenna matching circuitry 20 and the first traditional RFtransmit circuitry 24.

The traditional communications circuitry 10 illustrated in FIG. 2 may beused as a TDD system or a simplex system. However, the traditionalcommunications circuitry 10 illustrated in FIG. 2 may also be used as afrequency-division duplex (FDD) system, which is capable of transmittingand receiving RF signals simultaneously. Such a system may also becalled a full-duplex system.

When the traditional communications circuitry 10 is transmitting RFsignals via the first RF antenna 16, the traditional RF system controlcircuitry 12 provides the first traditional upstream transmit signalTUT1 to the first traditional RF transmit circuitry 24, which providesthe traditional transmit signal TTX to the first RF antenna 16 via firsttraditional RF duplexer 30 based on the first traditional upstreamtransmit signal TUT1.

When the traditional communications circuitry 10 is receiving RF signalsvia the first RF antenna 16, the first traditional antenna matchingcircuitry 20 receives the RF signals from the first RF antenna 16 andforwards the RF signals via the first traditional RF duplexer 30 to thefirst traditional RF receive circuitry 22. As such, the firsttraditional RF duplexer 30 provides the traditional receive signal TRXto the first traditional RF receive circuitry 22, which provides thefirst traditional downstream receive signal TDR1 to the traditional RFsystem control circuitry 12 based on the traditional receive signal TRX.

The first traditional RF duplexer 30 provides filtering, such that thefirst traditional RF receive circuitry 22 and the first traditional RFtransmit circuitry 24 are substantially isolated from one another. Assuch, the first traditional RF receive circuitry 22 and the firsttraditional RF transmit circuitry 24 are prevented from interfering withone another. Traditional FDD systems using duplexers with high rejectionratios have a fixed frequency transfer. Covering multiple communicationsbands requires multiple duplexers and switches to route RF signalsthrough appropriate signal paths.

FIG. 3 shows the traditional communications circuitry 10 according tothe prior art. The traditional communications circuitry 10 illustratedin FIG. 3 is a carrier aggregation (CA) based system, which is capableof transmitting or receiving multiple simultaneous transmit signals ormultiple simultaneous receive signals, respectively, or both. Each ofthe simultaneous transmit signals is in a frequency band that isdifferent from each frequency band of a balance of the simultaneoustransmit signals. Similarly, each of the simultaneous receive signals isin a frequency band that is different from each frequency band of abalance of the simultaneous receive signals. The traditionalcommunications circuitry 10 may operate as a simplex system, ahalf-duplex system, or a full-duplex system.

The traditional communications circuitry 10 includes the traditional RFsystem control circuitry 12, the traditional RF front-end circuitry 14,the first RF antenna 16, and a second RF antenna 32. The traditional RFfront-end circuitry 14 includes the first traditional antenna matchingcircuitry 20, the first traditional RF receive circuitry 22, the firsttraditional RF transmit circuitry 24, the first traditional RF duplexer30, first traditional antenna switching circuitry 34, a secondtraditional RF duplexer 36, a third traditional RF duplexer 38, secondtraditional antenna matching circuitry 40, second traditional antennaswitching circuitry 42, a fourth traditional RF duplexer 44, a fifthtraditional RF duplexer 46, a sixth traditional RF duplexer 48, secondtraditional RF receive circuitry 50, and second traditional RF transmitcircuitry 52. Traditional CA systems use fixed frequency filters anddiplexers, triplexers, or both to combine signal paths, which increasescomplexity. Alternatively, additional switch paths may be used, but maydegrade performance.

The first traditional antenna matching circuitry 20 is coupled betweenthe first RF antenna 16 and the first traditional antenna switchingcircuitry 34. The second traditional antenna matching circuitry 40 iscoupled between the second RF antenna 32 and the second traditionalantenna switching circuitry 42. The first traditional RF duplexer 30 iscoupled between the first traditional antenna switching circuitry 34 andthe first traditional RF receive circuitry 22, and is further coupledbetween the first traditional antenna switching circuitry 34 and thefirst traditional RF transmit circuitry 24. The second traditional RFduplexer 36 is coupled between the first traditional antenna switchingcircuitry 34 and the first traditional RF receive circuitry 22, and isfurther coupled between the first traditional antenna switchingcircuitry 34 and the first traditional RF transmit circuitry 24. Thethird traditional RF duplexer 38 is coupled between the firsttraditional antenna switching circuitry 34 and the first traditional RFreceive circuitry 22, and is further coupled between the firsttraditional antenna switching circuitry 34 and the first traditional RFtransmit circuitry 24.

The fourth traditional RF duplexer 44 is coupled between the secondtraditional antenna switching circuitry 42 and the second traditional RFreceive circuitry 50, and is further coupled between the secondtraditional antenna switching circuitry 42 and the second traditional RFtransmit circuitry 52. The fifth traditional RF duplexer 46 is coupledbetween the second traditional antenna switching circuitry 42 and thesecond traditional RF receive circuitry 50, and is further coupledbetween the second traditional antenna switching circuitry 42 and thesecond traditional RF transmit circuitry 52. The sixth traditional RFduplexer 48 is coupled between the second traditional antenna switchingcircuitry 42 and the second traditional RF receive circuitry 50, and isfurther coupled between the second traditional antenna switchingcircuitry 42 and the second traditional RF transmit circuitry 52.

The first traditional RF duplexer 30 is associated with a firstaggregated receive band, a first aggregated transmit band, or both. Thesecond traditional RF duplexer 36 is associated with a second aggregatedreceive band, a second aggregated transmit band, or both. The thirdtraditional RF duplexer 38 is associated with a third aggregated receiveband, a third aggregated transmit band, or both. The fourth traditionalRF duplexer 44 is associated with a fourth aggregated receive band, afourth aggregated transmit band, or both. The fifth traditional RFduplexer 46 is associated with a fifth aggregated receive band, a fifthaggregated transmit band, or both. The sixth traditional RF duplexer 48is associated with a sixth aggregated receive band, a sixth aggregatedtransmit band, or both.

The first traditional antenna switching circuitry 34 couples a selectedone of the first traditional RF duplexer 30, the second traditional RFduplexer 36, and the third traditional RF duplexer 38 to the firsttraditional antenna matching circuitry 20. Therefore, the first RFantenna 16 is associated with a selected one of the first aggregatedreceive band, the second aggregated receive band, and the thirdaggregated receive band; with a selected one of the first aggregatedtransmit band, the second aggregated transmit band, and the thirdaggregated transmit band; or both.

Similarly, the second traditional antenna switching circuitry 42 couplesa selected one of the fourth traditional RF duplexer 44, the fifthtraditional RF duplexer 46, and the sixth traditional RF duplexer 48 tothe second traditional antenna matching circuitry 40. Therefore, thesecond RF antenna 32 is associated with a selected one of the fourthaggregated receive band, the fifth aggregated receive band, and thesixth aggregated receive band; with a selected one of the fourthaggregated transmit band, the fifth aggregated transmit band, and thesixth aggregated transmit band; or both.

During transmit CA, the traditional RF system control circuitry 12provides the first traditional upstream transmit signal TUT1 to thefirst traditional RF transmit circuitry 24, which forwards the firsttraditional upstream transmit signal TUT1 to the first RF antenna 16 fortransmission via the selected one of the first traditional RF duplexer30, the second traditional RF duplexer 36, and the third traditional RFduplexer 38; via the first traditional antenna switching circuitry 34;and via the first traditional antenna matching circuitry 20.

Additionally, during transmit CA, the traditional RF system controlcircuitry 12 provides a second traditional upstream transmit signal TUT2to the second traditional RF transmit circuitry 52, which forwards thesecond traditional upstream transmit signal TUT2 to the second RFantenna 32 for transmission via the selected one of the fourthtraditional RF duplexer 44, the fifth traditional RF duplexer 46, andthe sixth traditional RF duplexer 48; via the second traditional antennaswitching circuitry 42; and via the second traditional antenna matchingcircuitry 40.

During receive CA, the first RF antenna 16 forwards a received RF signalto the first traditional RF receive circuitry 22 via the firsttraditional antenna matching circuitry 20, the first traditional antennaswitching circuitry 34, and the selected one of the first traditional RFduplexer 30, the second traditional RF duplexer 36, and the thirdtraditional RF duplexer 38. The first traditional RF receive circuitry22 provides the first traditional downstream receive signal TDR1 to thetraditional RF system control circuitry 12 based on the received RFsignal.

Additionally, during receive CA, the second RF antenna 32 forwards areceived RF signal to the second traditional RF receive circuitry 50 viathe second traditional antenna matching circuitry 40, the secondtraditional antenna switching circuitry 42, and the selected one of thefourth traditional RF duplexer 44, the fifth traditional RF duplexer 46,and the sixth traditional RF duplexer 48. The second traditional RFreceive circuitry 50 provides a second traditional downstream receivesignal TDR2 to the traditional RF system control circuitry 12 based onthe received RF signal.

Since only the selected one of the first traditional RF duplexer 30, thesecond traditional RF duplexer 36, and the third traditional RF duplexer38 is coupled to the first traditional antenna matching circuitry 20;the first traditional antenna switching circuitry 34 isolates each ofthe first traditional RF duplexer 30, the second traditional RF duplexer36, and the third traditional RF duplexer 38 from one another; andprevents each of the first traditional RF duplexer 30, the secondtraditional RF duplexer 36, and the third traditional RF duplexer 38from interfering with one another.

Similarly, since only the selected one of the fourth traditional RFduplexer 44, the fifth traditional RF duplexer 46, and the sixthtraditional RF duplexer 48 is coupled to the second traditional antennamatching circuitry 40; the second traditional antenna matching circuitry40 isolates each of the fourth traditional RF duplexer 44, the fifthtraditional RF duplexer 46, and the sixth traditional RF duplexer 48from one another; and prevents each of the fourth traditional RFduplexer 44, the fifth traditional RF duplexer 46, and the sixthtraditional RF duplexer 48 from interfering with one another.

FIG. 4 shows RF communications circuitry 54 according to one embodimentof the RF communications circuitry 54. The RF communications circuitry54 includes RF system control circuitry 56, RF front-end circuitry 58,and the first RF antenna 16. The RF front-end circuitry 58 includes afirst RF filter structure 60, RF receive circuitry 62, and RF transmitcircuitry 64. The first RF filter structure 60 includes a first tunableRF filter path 66 and a second tunable RF filter path 68. Additionally,the first RF filter structure 60 has a first connection node 70, asecond connection node 72, and a first common connection node 74. In oneembodiment of the RF system control circuitry 56, the RF system controlcircuitry 56 is an RF transceiver. In one embodiment of the firsttunable RF filter path 66, the first tunable RF filter path 66 includesa pair of weakly coupled resonators R(1,1), R(1,2) (FIG. 22). As such,in one embodiment of the first RF filter structure 60, the RF filterstructure 60 includes the pair of weakly coupled resonators R(1,1),R(1,2) (FIG. 21).

In alternate embodiments of the first RF filter structure 60, any or allof the first connection node 70, the second connection node 72, and thefirst common connection node 74 are external to the first RF filterstructure 60. In one embodiment of the first tunable RF filter path 66,the first tunable RF filter path 66 includes a first pair (not shown) ofweakly coupled resonators. In one embodiment of the second tunable RFfilter path 68, the second tunable RF filter path 68 includes a secondpair (not shown) of weakly coupled resonators.

In one embodiment of the first RF filter structure 60, the first tunableRF filter path 66 is directly coupled between the first commonconnection node 74 and the first connection node 70, the second tunableRF filter path 68 is directly coupled between the second connection node72 and the first common connection node 74, and the first RF antenna 16is directly coupled to the first common connection node 74. In anotherembodiment of the RF communications circuitry 54, the first RF antenna16 is omitted. Additionally, the RF receive circuitry 62 is coupledbetween the first connection node 70 and the RF system control circuitry56, and the RF transmit circuitry 64 is coupled between the secondconnection node 72 and the RF system control circuitry 56.

In one embodiment of the RF communications circuitry 54, the firsttunable RF filter path 66 is a first RF receive filter, such that thefirst RF antenna 16 forwards a received RF signal via the first commonconnection node 74 to provide a first upstream RF receive signal RU1 tothe first tunable RF filter path 66, which receives and filters thefirst upstream RF receive signal RU1 to provide a first filtered RFreceive signal RF1 to the RF receive circuitry 62. The RF receivecircuitry 62 may include down-conversion circuitry, amplificationcircuitry, power supply circuitry, filtering circuitry, switchingcircuitry, combining circuitry, splitting circuitry, dividing circuitry,clocking circuitry, the like, or any combination thereof. The RF receivecircuitry 62 processes the first filtered RF receive signal RF1 toprovide a first receive signal RX1 to the RF system control circuitry56.

In one embodiment of the RF communications circuitry 54, the secondtunable RF filter path 68 is a first RF transmit filter, such that theRF system control circuitry 56 provides a first transmit signal TX1 tothe RF transmit circuitry 64, which processes the first transmit signalTX1 to provide a first upstream RF transmit signal TU1 to the secondtunable RF filter path 68. The RF transmit circuitry 64 may includeup-conversion circuitry, amplification circuitry, power supplycircuitry, filtering circuitry, switching circuitry, combiningcircuitry, splitting circuitry, dividing circuitry, clocking circuitry,the like, or any combination thereof. The second tunable RF filter path68 receives and filters the first upstream RF transmit signal TU1 toprovide a first filtered RF transmit signal TF1, which is transmittedvia the first common connection node 74 by the first RF antenna 16.

The RF system control circuitry 56 provides a first filter controlsignal FCS1 to the first tunable RF filter path 66 and provides a secondfilter control signal FCS2 to the second tunable RF filter path 68. Assuch, in one embodiment of the RF communications circuitry 54, the RFsystem control circuitry 56 tunes a first filter parameter of the firsttunable RF filter path 66 using the first filter control signal FCS1.Additionally, the RF system control circuitry 56 tunes a first filterparameter of the second tunable RF filter path 68 using the secondfilter control signal FCS2.

In one embodiment of the RF communications circuitry 54, the firsttunable RF filter path 66 and the second tunable RF filter path 68 donot significantly load one another at frequencies of interest. As such,by directly coupling the first tunable RF filter path 66 and the secondtunable RF filter path 68 to the first common connection node 74;front-end RF switching elements may be avoided, thereby reducing cost,size, and non-linearity; and increasing efficiency and flexibility ofthe RF communications circuitry 54. Since tunable RF filters can supportmultiple communications bands using a single signal path, they cansimplify front-end architectures by eliminating switching and duplexingcomponents.

In one embodiment of the RF communications circuitry 54, the RFcommunications circuitry 54 is used as an FDD communications system,such that the first upstream RF receive signal RU1 and the firstfiltered RF transmit signal TF1 are full-duplex signals. In an alternateembodiments of the RF communications circuitry 54, the RF communicationscircuitry 54 is used as a TDD communications system, such that the firstupstream RF receive signal RU1 and the first filtered RF transmit signalTF1 are half-duplex signals. In additional embodiments of the RFcommunications circuitry 54, the RF communications circuitry 54 is usedas a simplex communications system, such that the first upstream RFreceive signal RU1 is a simplex signal and the first filtered RFtransmit signal TF1 is not present. In other embodiments of the RFcommunications circuitry 54, the RF communications circuitry 54 is usedas a simplex communications system, such that the first upstream RFreceive signal RU1 is not present and the first filtered RF transmitsignal TF1 is a simplex signal.

FIG. 5 is a graph illustrating filtering characteristics of the firsttunable RF filter path 66 and the second tunable RF filter path 68illustrated in FIG. 4 according to one embodiment of the first tunableRF filter path 66 and the second tunable RF filter path 68. The firsttunable RF filter path 66 is a first RF bandpass filter, which functionsas the first RF receive filter, and the second tunable RF filter path 68is a second RF bandpass filter, which functions as the first RF transmitfilter. A bandwidth 76 of the first RF bandpass filter, a centerfrequency 78 of the first RF bandpass filter, a bandwidth 80 of thesecond RF bandpass filter, a center frequency 82 of the second RFbandpass filter, a frequency 84 of the first upstream RF receive signalRU1 (FIG. 4), and a frequency 86 of the first filtered RF transmitsignal TF1 (FIG. 4) are shown. Operation of the first RF bandpass filterand the second RF bandpass filter is such that the first RF bandpassfilter and the second RF bandpass filter do not significantly interferewith one another. In this regard, the bandwidth 76 of the first RFbandpass filter does not overlap the bandwidth 80 of the second RFbandpass filter.

In one embodiment of the first RF receive filter and the first RFtransmit filter, the first RF receive filter and the first RF transmitfilter in combination function as an RF duplexer. As such, a duplexfrequency 88 of the RF duplexer is about equal to a difference betweenthe frequency 84 of the first upstream RF receive signal RU1 (FIG. 4)and the frequency 86 of the first filtered RF transmit signal TF1 (FIG.4).

In one embodiment of the first tunable RF filter path 66, the firstfilter parameter of the first tunable RF filter path 66 is tunable basedon the first filter control signal FCS1. In an alternate embodiment ofthe first tunable RF filter path 66, both the first filter parameter ofthe first tunable RF filter path 66 and a second filter parameter of thefirst tunable RF filter path 66 are tunable based on the first filtercontrol signal FCS1. Similarly, in one embodiment of the second tunableRF filter path 68, the first filter parameter of the second tunable RFfilter path 68 is tunable based on the second filter control signalFCS2. In an alternate embodiment of the second tunable RF filter path68, both the first filter parameter of the second tunable RF filter path68 and a second filter parameter of the second tunable RF filter path 68are tunable based on the second filter control signal FCS2.

The first filter parameter of the first tunable RF filter path 66 is thecenter frequency 78 of the first RF bandpass filter. The second filterparameter of the first tunable RF filter path 66 is the bandwidth 76 ofthe first RF bandpass filter. The first filter parameter of the secondtunable RF filter path 68 is the center frequency 82 of the second RFbandpass filter. The second filter parameter of the second tunable RFfilter path 68 is the bandwidth 80 of the second RF bandpass filter.

FIGS. 6A and 6B are graphs illustrating filtering characteristics of thefirst tunable RF filter path 66 and the second tunable RF filter path68, respectively, illustrated in FIG. 4 according to an alternateembodiment of the first tunable RF filter path 66 and the second tunableRF filter path 68, respectively. The first tunable RF filter path 66 isan RF lowpass filter and the second tunable RF filter path 68 is an RFhighpass filter. FIG. 6A shows a frequency response curve 90 of the RFlowpass filter and FIG. 6B shows a frequency response curve 92 of the RFhighpass filter. Additionally FIG. 6A shows a break frequency 94 of theRF lowpass filter and FIG. 6B shows a break frequency 96 of the RFhighpass filter. Both FIGS. 6A and 6B show the frequency 84 of the firstupstream RF receive signal RU1 (FIG. 4), the frequency 86 of the firstfiltered RF transmit signal TF1 (FIG. 4), and the duplex frequency 88 ofthe RF duplexer for clarification. However, the RF lowpass filter andthe RF highpass filter in combination function as an RF diplexer. Thefirst filter parameter of the first tunable RF filter path 66 is thebreak frequency 94 of the RF lowpass filter. In one embodiment of the RFlowpass filter, the RF lowpass filter has bandpass filtercharacteristics. The first filter parameter of the second tunable RFfilter path 68 is the break frequency 96 of the RF highpass filter. Inone embodiment of the RF highpass filter, the RF highpass filter hasbandpass filter characteristics. In one embodiment of the RF diplexer,the break frequency 96 of the RF highpass filter is about equal to thebreak frequency 94 of the RF lowpass filter.

FIG. 7 shows the RF communications circuitry 54 according to oneembodiment of the RF communications circuitry 54. The RF communicationscircuitry 54 illustrated in FIG. 7 is similar to the RF communicationscircuitry 54 illustrated in FIG. 4, except in the RF front-end circuitry58 illustrated in FIG. 7, the RF transmit circuitry 64 (FIG. 4) isomitted and the RF front-end circuitry 58 further includes RF front-endcontrol circuitry 98.

The RF system control circuitry 56 provides a front-end control signalFEC to the RF front-end control circuitry 98. The RF front-end controlcircuitry 98 provides the first filter control signal FCS1 and thesecond filter control signal FCS2 based on the front-end control signalFEC. In the RF communications circuitry 54 illustrated in FIG. 4, the RFsystem control circuitry 56 provides the first filter control signalFCS1 and the second filter control signal FCS2 directly. In general, theRF communications circuitry 54 includes control circuitry, which may beeither the RF system control circuitry 56 or the RF front-end controlcircuitry 98, that provides the first filter control signal FCS1 and thesecond filter control signal FCS2. As such, in one embodiment of the RFcommunications circuitry 54, the control circuitry tunes a first filterparameter of the first tunable RF filter path 66 using the first filtercontrol signal FCS1. Additionally, the control circuitry tunes a firstfilter parameter of the second tunable RF filter path 68 using thesecond filter control signal FCS2. In an additional embodiment of the RFcommunications circuitry 54, the control circuitry further tunes asecond filter parameter of the first tunable RF filter path 66 using thefirst filter control signal FCS1; and the control circuitry furthertunes a second filter parameter of the second tunable RF filter path 68using the second filter control signal FCS2.

In alternate embodiments of the first RF filter structure 60, any or allof the first connection node 70, the second connection node 72, and thefirst common connection node 74 are external to the first RF filterstructure 60. In one embodiment of the first tunable RF filter path 66,the first tunable RF filter path 66 includes a first pair (not shown) ofweakly coupled resonators. In one embodiment of the second tunable RFfilter path 68, the second tunable RF filter path 68 includes a secondpair (not shown) of weakly coupled resonators.

In one embodiment of the first RF filter structure 60, the first tunableRF filter path 66 is directly coupled between the first commonconnection node 74 and the first connection node 70, the second tunableRF filter path 68 is directly coupled between the second connection node72 and the first common connection node 74, and the first RF antenna 16is directly coupled to the first common connection node 74. In anotherembodiment of the RF communications circuitry 54, the first RF antenna16 is omitted. Additionally, the RF receive circuitry 62 is coupledbetween the first connection node 70 and the RF system control circuitry56, and the RF receive circuitry 62 is further coupled between thesecond connection node 72 and the RF system control circuitry 56.

In one embodiment of the RF communications circuitry 54, the firsttunable RF filter path 66 is a first RF receive filter, such that thefirst RF antenna 16 forwards a first received RF signal via the firstcommon connection node 74 to provide a first upstream RF receive signalRU1 to the first tunable RF filter path 66, which receives and filtersthe first upstream RF receive signal RU1 to provide a first filtered RFreceive signal RF1 to the RF receive circuitry 62. Additionally, thesecond tunable RF filter path 68 is a second RF receive filter, suchthat the first RF antenna 16 forwards a second received RF signal viathe first common connection node 74 to provide a second upstream RFreceive signal RU2 to the second tunable RF filter path 68, whichreceives and filters the second upstream RF receive signal RU2 toprovide a second filtered RF receive signal RF2 to the RF receivecircuitry 62.

The RF receive circuitry 62 may include down-conversion circuitry,amplification circuitry, power supply circuitry, filtering circuitry,switching circuitry, combining circuitry, splitting circuitry, dividingcircuitry, clocking circuitry, the like, or any combination thereof. TheRF receive circuitry 62 processes the first filtered RF receive signalRF1 to provide a first receive signal RX1 to the RF system controlcircuitry 56. Additionally, the RF receive circuitry 62 processes thesecond filtered RF receive signal RF2 to provide a second receive signalRX2 to the RF system control circuitry 56.

In one embodiment of the RF communications circuitry 54, the firsttunable RF filter path 66 and the second tunable RF filter path 68 donot significantly load one another at frequencies of interest. As such,by directly coupling the first tunable RF filter path 66 and the secondtunable RF filter path 68 to the first common connection node 74;front-end RF switching elements may be avoided, thereby reducing cost,size, and non-linearity; and increasing efficiency and flexibility ofthe RF communications circuitry 54.

In this regard, in one embodiment of the first tunable RF filter path 66and the second tunable RF filter path 68, each of the first tunable RFfilter path 66 and the second tunable RF filter path 68 is a bandpassfilter having a unique center frequency. As such, the first filterparameter of each of the first tunable RF filter path 66 and the secondtunable RF filter path 68 is a unique center frequency.

In an alternate embodiment of the first tunable RF filter path 66 andthe second tunable RF filter path 68, one of the first tunable RF filterpath 66 and the second tunable RF filter path 68 is a lowpass filter,and another of the first tunable RF filter path 66 and the secondtunable RF filter path 68 is a highpass filter. As such, the firstfilter parameter of each of the first tunable RF filter path 66 and thesecond tunable RF filter path 68 is a break frequency.

In an additional embodiment of the first tunable RF filter path 66 andthe second tunable RF filter path 68, one of the first tunable RF filterpath 66 and the second tunable RF filter path 68 is a lowpass filter,and another of the first tunable RF filter path 66 and the secondtunable RF filter path 68 is a bandpass filter. As such, the firstfilter parameter of one of the first tunable RF filter path 66 and thesecond tunable RF filter path 68 is a center frequency, and the firstfilter parameter of another of the first tunable RF filter path 66 andthe second tunable RF filter path 68 is a break frequency.

In an additional embodiment of the first tunable RF filter path 66 andthe second tunable RF filter path 68, one of the first tunable RF filterpath 66 and the second tunable RF filter path 68 is a highpass filter,and another of the first tunable RF filter path 66 and the secondtunable RF filter path 68 is a bandpass filter. As such, the firstfilter parameter of one of the first tunable RF filter path 66 and thesecond tunable RF filter path 68 is a center frequency, and the firstfilter parameter of another of the first tunable RF filter path 66 andthe second tunable RF filter path 68 is a break frequency.

In one embodiment of the RF communications circuitry 54, the RFcommunications circuitry 54 is a receive only CA system, such that thefirst tunable RF filter path 66, which is the first RF receive filter,and the second tunable RF filter path 68, which is the second RF receivefilter, simultaneously receive and filter the first upstream RF receivesignal RU1 and the second upstream RF receive signal RU2, respectively,via the first common connection node 74. As such, the first RF filterstructure 60 functions as a de-multiplexer. In this regard, each of thefirst upstream RF receive signal RU1 and the second upstream RF receivesignal RU2 has a unique carrier frequency. Using receive CA may increasean effective receive bandwidth of the RF communications circuitry 54.

In another embodiment of the RF communications circuitry 54, the RFcommunications circuitry 54 is a receive only communications system,such that the first tunable RF filter path 66, which is the first RFreceive filter, and the second tunable RF filter path 68, which is thesecond RF receive filter, do not simultaneously receive and filter thefirst upstream RF receive signal RU1 and the second upstream RF receivesignal RU2, respectively. As such, the first upstream RF receive signalRU1 and the second upstream RF receive signal RU2 are nonsimultaneoussignals. Each of the first upstream RF receive signal RU1 and the secondupstream RF receive signal RU2 may be associated with a unique RFcommunications band.

FIG. 8 shows the RF communications circuitry 54 according to analternate embodiment of the RF communications circuitry 54. The RFcommunications circuitry 54 illustrated in FIG. 8 is similar to the RFcommunications circuitry 54 illustrated in FIG. 7, except in the RFfront-end circuitry 58 illustrated in FIG. 8, the RF receive circuitry62 is omitted and the RF transmit circuitry 64 is included.

The RF system control circuitry 56 provides the front-end control signalFEC to the RF front-end control circuitry 98. The RF front-end controlcircuitry 98 provides the first filter control signal FCS1 and thesecond filter control signal FCS2 based on the front-end control signalFEC. In the RF communications circuitry 54 illustrated in FIG. 4, the RFsystem control circuitry 56 provides the first filter control signalFCS1 and the second filter control signal FCS2 directly.

In general, the RF communications circuitry 54 includes controlcircuitry, which may be either the RF system control circuitry 56 or theRF front-end control circuitry 98, that provides the first filtercontrol signal FCS1 and the second filter control signal FCS2. As such,in one embodiment of the RF communications circuitry 54, the controlcircuitry tunes a first filter parameter of the first tunable RF filterpath 66 using the first filter control signal FCS1. Additionally, thecontrol circuitry tunes a first filter parameter of the second tunableRF filter path 68 using the second filter control signal FCS2. In anadditional embodiment of the RF communications circuitry 54, the controlcircuitry further tunes a second filter parameter of the first tunableRF filter path 66 using the first filter control signal FCS1; and thecontrol circuitry further tunes a second filter parameter of the secondtunable RF filter path 68 using the second filter control signal FCS2.

In alternate embodiments of the first RF filter structure 60, any or allof the first connection node 70, the second connection node 72, and thefirst common connection node 74 are external to the first RF filterstructure 60. In one embodiment of the first tunable RF filter path 66,the first tunable RF filter path 66 includes a first pair (not shown) ofweakly coupled resonators. In one embodiment of the second tunable RFfilter path 68, the second tunable RF filter path 68 includes a secondpair (not shown) of weakly coupled resonators.

In one embodiment of the first RF filter structure 60, the first tunableRF filter path 66 is directly coupled between the first commonconnection node 74 and the first connection node 70, the second tunableRF filter path 68 is directly coupled between the second connection node72 and the first common connection node 74, and the first RF antenna 16is directly coupled to the first common connection node 74. In anotherembodiment of the RF communications circuitry 54, the first RF antenna16 is omitted. Additionally, the RF transmit circuitry 64 is coupledbetween the first connection node 70 and the RF system control circuitry56, and the RF transmit circuitry 64 is further coupled between thesecond connection node 72 and the RF system control circuitry 56.

In one embodiment of the RF communications circuitry 54, the firsttunable RF filter path 66 is a first RF transmit filter, such that theRF system control circuitry 56 provides the first transmit signal TX1 tothe RF transmit circuitry 64, which processes the first transmit signalTX1 to provide a first upstream RF transmit signal TU1 to the firsttunable RF filter path 66. Similarly, the second tunable RF filter path68 is a second RF transmit filter, such that the RF system controlcircuitry 56 provides a second transmit signal TX2 to the RF transmitcircuitry 64, which processes the second transmit signal TX2 to providea second upstream RF transmit signal TU2 to the second tunable RF filterpath 68.

The RF transmit circuitry 64 may include up-conversion circuitry,amplification circuitry, power supply circuitry, filtering circuitry,switching circuitry, combining circuitry, splitting circuitry, dividingcircuitry, clocking circuitry, the like, or any combination thereof. Thefirst tunable RF filter path 66 receives and filters the first upstreamRF transmit signal TU1 to provide the first filtered RF transmit signalTF1, which is transmitted via the first common connection node 74 by thefirst RF antenna 16. Similarly, the second tunable RF filter path 68receives and filters the second upstream RF transmit signal TU2 toprovide a second filtered RF transmit signal TF2, which is transmittedvia the first common connection node 74 by the first RF antenna 16.

In one embodiment of the RF communications circuitry 54, the firsttunable RF filter path 66 and the second tunable RF filter path 68 donot significantly load one another at frequencies of interest. As such,by directly coupling the first tunable RF filter path 66 and the secondtunable RF filter path 68 to the first common connection node 74;front-end RF switching elements may be avoided, thereby reducing cost,size, and non-linearity; and increasing efficiency and flexibility ofthe RF communications circuitry 54.

In this regard, in one embodiment of the first tunable RF filter path 66and the second tunable RF filter path 68, each of the first tunable RFfilter path 66 and the second tunable RF filter path 68 is a bandpassfilter having a unique center frequency. As such, the first filterparameter of each of the first tunable RF filter path 66 and the secondtunable RF filter path 68 is a unique center frequency.

In an alternate embodiment of the first tunable RF filter path 66 andthe second tunable RF filter path 68, one of the first tunable RF filterpath 66 and the second tunable RF filter path 68 is a lowpass filter,and another of the first tunable RF filter path 66 and the secondtunable RF filter path 68 is a highpass filter. As such, the firstfilter parameter of each of the first tunable RF filter path 66 and thesecond tunable RF filter path 68 is a break frequency.

In an additional embodiment of the first tunable RF filter path 66 andthe second tunable RF filter path 68, one of the first tunable RF filterpath 66 and the second tunable RF filter path 68 is a lowpass filter,and another of the first tunable RF filter path 66 and the secondtunable RF filter path 68 is a bandpass filter. As such, the firstfilter parameter of one of the first tunable RF filter path 66 and thesecond tunable RF filter path 68 is a center frequency, and the firstfilter parameter of another of the first tunable RF filter path 66 andthe second tunable RF filter path 68 is a break frequency.

In an additional embodiment of the first tunable RF filter path 66 andthe second tunable RF filter path 68, one of the first tunable RF filterpath 66 and the second tunable RF filter path 68 is a highpass filter,and another of the first tunable RF filter path 66 and the secondtunable RF filter path 68 is a bandpass filter. As such, the firstfilter parameter of one of the first tunable RF filter path 66 and thesecond tunable RF filter path 68 is a center frequency, and the firstfilter parameter of another of the first tunable RF filter path 66 andthe second tunable RF filter path 68 is a break frequency.

In one embodiment of the RF communications circuitry 54, the RFcommunications circuitry 54 is a transmit only CA system, such that thefirst tunable RF filter path 66, which is the first RF transmit filter,and the second tunable RF filter path 68, which is the second RFtransmit filter, simultaneously receive and filter the first upstream RFtransmit signal TU1 and the second upstream RF transmit signal TU2,respectively, to simultaneously provide the first filtered RF transmitsignal TF1 and the second filtered RF transmit signal TF2, respectively,via the first common connection node 74. As such, the first RF filterstructure 60 functions as a multiplexer. In this regard, each of thefirst filtered RF transmit signal TF1 and the second filtered RFtransmit signal TF2 has a unique carrier frequency. Using transmit CAmay increase an effective transmit bandwidth of the RF communicationscircuitry 54.

In another embodiment of the RF communications circuitry 54, the RFcommunications circuitry 54 is a transmit only communications system,such that the first tunable RF filter path 66, which is the first RFtransmit filter, and the second tunable RF filter path 68, which is thesecond RF transmit filter, do not simultaneously receive and filter thefirst upstream RF transmit signal TU1 and the second upstream RFtransmit signal TU2, respectively. As such, the first filtered RFtransmit signal TF1 and the second filtered RF transmit signal TF2 arenonsimultaneous signals. Each of the first filtered RF transmit signalTF1 and the second filtered RF transmit signal TF2 may be associatedwith a unique RF communications band.

FIGS. 9A and 9B are graphs illustrating filtering characteristics of thefirst tunable RF filter path 66 and the second tunable RF filter path68, respectively, illustrated in FIG. 8 according to an additionalembodiment of the first tunable RF filter path 66 and the second tunableRF filter path 68, respectively. FIG. 9A shows a frequency responsecurve 100 of the first tunable RF filter path 66 and FIG. 9B shows afrequency response curve 102 of the second tunable RF filter path 68.The first tunable RF filter path 66 and the second tunable RF filterpath 68 are both bandpass filters having the frequency response curves100, 102 illustrated in FIGS. 9A and 9B, respectively. In this regard,the first tunable RF filter path 66 and the second tunable RF filterpath 68 can be directly coupled to one another via the first commonconnection node 74 (FIG. 8) without interfering with one another.

FIGS. 10A and 10B are graphs illustrating filtering characteristics ofthe first traditional RF duplexer 30 and the second traditional RFduplexer 36, respectively, illustrated in FIG. 3 according to the priorart. FIG. 10A shows a frequency response curve 104 of the firsttraditional RF duplexer 30 and FIG. 10B shows a frequency response curve106 of the second traditional RF duplexer 36. There is interference 108between the frequency response curve 104 of the first traditional RFduplexer 30 and the frequency response curve 106 of the secondtraditional RF duplexer 36 as shown in FIGS. 10A and 10B. In thisregard, the first traditional RF duplexer 30 and the second traditionalRF duplexer 36 cannot be directly coupled to one another withoutinterfering with one another. To avoid interference between differentfilters, traditional systems use RF switches to disconnect unusedfilters.

FIG. 11 shows the RF communications circuitry 54 according to oneembodiment of the RF communications circuitry 54. The RF communicationscircuitry 54 illustrated in FIG. 11 is similar to the RF communicationscircuitry 54 illustrated in FIG. 8, except in the RF communicationscircuitry 54 illustrated in FIG. 11, the RF front-end circuitry 58further includes the RF receive circuitry 62 and the first RF filterstructure 60 further includes a third tunable RF filter path 110 and afourth tunable RF filter path 112. Additionally, the RF front-endcircuitry 58 has the first connection node 70, the second connectionnode 72, the first common connection node 74, a third connection node114 and a fourth connection node 116, such that all of the firstconnection node 70, the second connection node 72, the first commonconnection node 74, the third connection node 114 and the fourthconnection node 116 are external to the first RF filter structure 60. Inan alternate of the RF front-end circuitry 58, any or all of the firstconnection node 70, the second connection node 72, the first commonconnection node 74, a third connection node 114 and a fourth connectionnode 116 are internal to the first RF filter structure 60.

The RF front-end control circuitry 98 further provides a third filtercontrol signal FCS3 to the third tunable RF filter path 110 and a fourthfilter control signal FCS4 to the fourth tunable RF filter path 112based on the front-end control signal FEC. In one embodiment of the RFcommunications circuitry 54, the control circuitry tunes a first filterparameter of the third tunable RF filter path 110 using the third filtercontrol signal FCS3. Additionally, the control circuitry tunes a firstfilter parameter of the fourth tunable RF filter path 112 using thefourth filter control signal FCS4. In an additional embodiment of the RFcommunications circuitry 54, the control circuitry further tunes asecond filter parameter of the third tunable RF filter path 110 usingthe third filter control signal FCS3; and the control circuitry furthertunes a second filter parameter of the fourth tunable RF filter path 112using the fourth filter control signal FCS4.

In one embodiment of the third tunable RF filter path 110, the thirdtunable RF filter path 110 includes a third pair (not shown) of weaklycoupled resonators. In one embodiment of the fourth tunable RF filterpath 112, the fourth tunable RF filter path 112 includes a fourth pair(not shown) of weakly coupled resonators.

In one embodiment of the third tunable RF filter path 110 and the fourthtunable RF filter path 112, the third tunable RF filter path 110 isdirectly coupled between the first common connection node 74 and thethird connection node 114, and the fourth tunable RF filter path 112 isdirectly coupled between the fourth connection node 116 and the firstcommon connection node 74. In another embodiment of the RFcommunications circuitry 54, the first RF antenna 16 is omitted.Additionally, the RF receive circuitry 62 is coupled between the thirdconnection node 114 and the RF system control circuitry 56, and the RFreceive circuitry 62 is further coupled between the fourth connectionnode 116 and the RF system control circuitry 56.

In one embodiment of the RF communications circuitry 54, the thirdtunable RF filter path 110 is the first RF receive filter, such that thefirst RF antenna 16 forwards a first received RF signal via the firstcommon connection node 74 to provide the first upstream RF receivesignal RU1 to the third tunable RF filter path 110, which receives andfilters the first upstream RF receive signal RU1 to provide the firstfiltered RF receive signal RF1 to the RF receive circuitry 62.Additionally, the fourth tunable RF filter path 112 is a second RFreceive filter, such that the first RF antenna 16 forwards a secondreceived RF signal via the first common connection node 74 to providethe second upstream RF receive signal RU2 to the fourth tunable RFfilter path 112, which receives and filters the second upstream RFreceive signal RU2 to provide the second filtered RF receive signal RF2to the RF receive circuitry 62.

The RF receive circuitry 62 may include down-conversion circuitry,amplification circuitry, power supply circuitry, filtering circuitry,switching circuitry, combining circuitry, splitting circuitry, dividingcircuitry, clocking circuitry, the like, or any combination thereof. TheRF receive circuitry 62 processes the first filtered RF receive signalRF1 to provide the first receive signal RX1 to the RF system controlcircuitry 56. Additionally, the RF receive circuitry 62 processes thesecond filtered RF receive signal RF2 to provide the second receivesignal RX2 to the RF system control circuitry 56.

In one embodiment of the RF communications circuitry 54, the firsttunable RF filter path 66, the second tunable RF filter path 68, thethird tunable RF filter path 110, and the fourth tunable RF filter path112 do not significantly load one another at frequencies of interest. Assuch, by directly coupling the first tunable RF filter path 66, thesecond tunable RF filter path 68, the third tunable RF filter path 110,and the fourth tunable RF filter path 112 to the first common connectionnode 74; front-end RF switching elements may be avoided, therebyreducing cost, size, and non-linearity; and increasing efficiency andflexibility of the RF communications circuitry 54.

In this regard, in one embodiment of the third tunable RF filter path110 and the fourth tunable RF filter path 112, each of the third tunableRF filter path 110 and the fourth tunable RF filter path 112 is abandpass filter having a unique center frequency. As such, the firstfilter parameter of each of the third tunable RF filter path 110 and thefourth tunable RF filter path 112 is a unique center frequency.

In an alternate embodiment of the third tunable RF filter path 110 andthe fourth tunable RF filter path 112, one of the third tunable RFfilter path 110 and the fourth tunable RF filter path 112 is a lowpassfilter, and another of the third tunable RF filter path 110 and thefourth tunable RF filter path 112 is a highpass filter. As such, thefirst filter parameter of each of the third tunable RF filter path 110and the fourth tunable RF filter path 112 is a break frequency.

In an additional embodiment of the third tunable RF filter path 110 andthe fourth tunable RF filter path 112, one of the third tunable RFfilter path 110 and the fourth tunable RF filter path 112 is a lowpassfilter, and another of the third tunable RF filter path 110 and thefourth tunable RF filter path 112 is a bandpass filter. As such, thefirst filter parameter of one of the third tunable RF filter path 110and the fourth tunable RF filter path 112 is a center frequency, and thefirst filter parameter of another of the third tunable RF filter path110 and the fourth tunable RF filter path 112 is a break frequency.

In an additional embodiment of the third tunable RF filter path 110 andthe fourth tunable RF filter path 112, one of the third tunable RFfilter path 110 and the fourth tunable RF filter path 112 is a highpassfilter, and another of the third tunable RF filter path 110 and thefourth tunable RF filter path 112 is a bandpass filter. As such, thefirst filter parameter of one of the third tunable RF filter path 110and the fourth tunable RF filter path 112 is a center frequency, and thefirst filter parameter of another of the third tunable RF filter path110 and the fourth tunable RF filter path 112 is a break frequency.

In one embodiment of the RF communications circuitry 54, the RFcommunications circuitry 54 is a CA system, such that the third tunableRF filter path 110, which is the first RF receive filter, and the fourthtunable RF filter path 112, which is the second RF receive filter,simultaneously receive and filter the first upstream RF receive signalRU1 and the second upstream RF receive signal RU2, respectively, via thefirst common connection node 74. As such, the first RF filter structure60 functions as a de-multiplexer using the third tunable RF filter path110 and the fourth tunable RF filter path 112. In one embodiment of thefirst RF filter structure 60, the first RF filter structure 60 furtherfunctions as a multiplexer using the first tunable RF filter path 66 andthe second tunable RF filter path 68. In this regard, each of the firstupstream RF receive signal RU1 and the second upstream RF receive signalRU2 has a unique carrier frequency.

In another embodiment of the RF communications circuitry 54, the RFcommunications circuitry 54 is a receive communications system, suchthat the third tunable RF filter path 110, which is the first RF receivefilter, and the fourth tunable RF filter path 112, which is the secondRF receive filter, do not simultaneously receive and filter the firstupstream RF receive signal RU1 and the second upstream RF receive signalRU2, respectively. As such, the first upstream RF receive signal RU1 andthe second upstream RF receive signal RU2 are nonsimultaneous signals.Each of the first upstream RF receive signal RU1 and the second upstreamRF receive signal RU2 may be associated with a unique RF communicationsband.

FIG. 12 shows the RF communications circuitry 54 according to analternate embodiment of the RF communications circuitry 54. The RFcommunications circuitry 54 illustrated in FIG. 12 is similar to the RFcommunications circuitry 54 illustrated in FIG. 11, except the RFcommunications circuitry 54 illustrated in FIG. 12 further includes thesecond RF antenna 32. Additionally, the RF front-end circuitry 58further includes a second common connection node 118 and a second RFfilter structure 120. The third tunable RF filter path 110 and thefourth tunable RF filter path 112 are included in the second RF filterstructure 120 instead of being included in the first RF filter structure60. Instead of being coupled to the first common connection node 74, thethird tunable RF filter path 110 and the fourth tunable RF filter path112 are coupled to the second common connection node 118. In oneembodiment of the third tunable RF filter path 110 and the fourthtunable RF filter path 112, the third tunable RF filter path 110 and thefourth tunable RF filter path 112 are directly coupled to the secondcommon connection node 118. In one embodiment of the RF communicationscircuitry 54, the second RF antenna 32 is coupled to the second commonconnection node 118.

FIG. 13 shows the RF communications circuitry 54 according to anadditional embodiment of the RF communications circuitry 54. The RFcommunications circuitry 54 illustrated in FIG. 13 is similar to the RFcommunications circuitry 54 illustrated in FIG. 12, except in the RFcommunications circuitry 54 illustrated in FIG. 13, the RF front-endcontrol circuitry 98 provides a front-end status signal FES to the RFsystem control circuitry 56. Additionally, the RF front-end controlcircuitry 98 provides a first calibration control signal CCS1 and up toand including an N^(TH) calibration control signal CCSN to the first RFfilter structure 60. The RF front-end control circuitry 98 provides aP^(TH) calibration control signal CCSP and up to and including an X^(TH)calibration control signal CCSX to the second RF filter structure 120.Details of the first RF filter structure 60 and the second RF filterstructure 120 are not shown to simplify FIG. 13.

The first RF filter structure 60 provides a first calibration statussignal CSS1 and up to and including a Q^(TH) calibration status signalCSSQ to the RF front-end control circuitry 98. The second RF filterstructure 120 provides an R^(TH) calibration status signal CSSR and upto and including a Y^(TH) calibration status signal CSSY to the RFfront-end control circuitry 98. In an alternate embodiment of the RFfront-end circuitry 58, any or all of the N^(TH) calibration controlsignal CCSN, the Q^(TH) calibration status signal CSSQ, the X^(TH)calibration control signal CCSX, and the Y^(TH) calibration statussignal CSSY are omitted.

In one embodiment of the RF front-end circuitry 58, the RF front-endcircuitry 58 operates in one of a normal operating mode and acalibration mode. During the calibration mode, the RF front-end controlcircuitry 98 performs a calibration of the first RF filter structure 60,the second RF filter structure 120, or both. As such, the RF front-endcontrol circuitry 98 provides any or all of the filter control signalsFCS1, FCS2, FCS3, FCS4 and any or all of the calibration control signalsCCS1, CCSN, CCSP, CCSX needed for calibration. Further, the RF front-endcontrol circuitry 98 receives any or all of the calibration statussignals CSS1, CSSQ, CSSR, CSSY needed for calibration.

During the normal operating mode, the RF front-end control circuitry 98provides any or all of the filter control signals FCS1, FCS2, FCS3, FCS4and any or all of the calibration control signals CCS1, CCSN, CCSP, CCSXneeded for normal operation. Further, the RF front-end control circuitry98 receives any or all of the calibration status signals CSS1, CSSQ,CSSR, CSSY needed for normal operation. Any or all of the calibrationcontrol signals CCS1, CCSN, CCSP, CCSX may be based on the front-endcontrol signal FEC. The front-end status signal FES may be based on anyor all of the calibration status signals CSS1, CSSQ, CSSR, CSSY.Further, during the normal operating mode, the RF front-end circuitry 58processes signals as needed for normal operation. Other embodimentsdescribed in the present disclosure may be associated with normaloperation.

The RF communications circuitry 54 illustrated in FIG. 13 includes thefirst RF antenna 16 and the second RF antenna 32. In general, the RFcommunications circuitry 54 is a multiple antenna system. A single-inputsingle-output (SISO) antenna system is a system in which RF transmitsignals may be transmitted from the first RF antenna 16 and RF receivesignals may be received via the second RF antenna 32. In one embodimentof the RF communications circuitry 54, the antenna system in the RFcommunications circuitry 54 is a SISO antenna system, as illustrated inFIG. 13.

A single-input multiple-output (SIMO) antenna system is a system inwhich RF transmit signals may be simultaneously transmitted from thefirst RF antenna 16 and the second RF antenna 32, and RF receive signalsmay be received via the second RF antenna 32. In an alternate embodimentof the RF communications circuitry 54, the second RF filter structure120 is coupled to the RF transmit circuitry 64, such that the antennasystem in the RF communications circuitry 54 is a SIMO antenna system.

A multiple-input single-output (MISO) antenna system is a system inwhich RF transmit signals may be transmitted from the first RF antenna16, and RF receive signals may be simultaneously received via the firstRF antenna 16 and the second RF antenna 32. In an additional embodimentof the RF communications circuitry 54, the first RF filter structure 60is coupled to the RF receive circuitry 62, such that the antenna systemin the RF communications circuitry 54 is a MISO antenna system.

A multiple-input multiple-output (MIMO) antenna system is a system inwhich RF transmit signals may be simultaneously transmitted from thefirst RF antenna 16 and the second RF antenna 32, and RF receive signalsmay be simultaneously received via the first RF antenna 16 and thesecond RF antenna 32. In another embodiment of the RF communicationscircuitry 54, the second RF filter structure 120 is coupled to the RFtransmit circuitry 64 and the first RF filter structure 60 is coupled tothe RF receive circuitry 62, such that the antenna system in the RFcommunications circuitry 54 is a MIMO antenna system.

FIG. 14 shows the RF communications circuitry 54 according to anotherembodiment of the RF communications circuitry 54. The RF communicationscircuitry 54 illustrated in FIG. 14 is similar to the RF communicationscircuitry 54 illustrated in FIG. 11, except in the RF communicationscircuitry 54 illustrated in FIG. 14, the first RF filter structure 60further includes a fifth tunable RF filter path 122 and a sixth tunableRF filter path 124, and the RF front-end circuitry 58 further includes afifth connection node 126 and a sixth connection node 128. Additionally,the RF front-end control circuitry 98 shown in FIG. 11 is not shown inFIG. 14 to simplify FIG. 14.

In one embodiment of the fifth tunable RF filter path 122, the fifthtunable RF filter path 122 includes a fifth pair (not shown) of weaklycoupled resonators. In one embodiment of the sixth tunable RF filterpath 124, the sixth tunable RF filter path 124 includes a sixth pair(not shown) of weakly coupled resonators.

In one embodiment of the fifth tunable RF filter path 122 and the sixthtunable RF filter path 124, the fifth tunable RF filter path 122 isdirectly coupled between the first common connection node 74 and thefifth connection node 126, and the sixth tunable RF filter path 124 isdirectly coupled between the sixth connection node 128 and the firstcommon connection node 74. In another embodiment of the RFcommunications circuitry 54, the first RF antenna 16 is omitted.Additionally, the RF receive circuitry 62 is further coupled between thesixth connection node 128 and the RF system control circuitry 56, andthe RF transmit circuitry 64 is further coupled between the fifthconnection node 126 and the RF system control circuitry 56.

In one embodiment of the RF communications circuitry 54, the sixthtunable RF filter path 124 is a third RF receive filter, such that thefirst RF antenna 16 forwards a third received RF signal via the firstcommon connection node 74 to provide a third upstream RF receive signalRU3 to the sixth tunable RF filter path 124, which receives and filtersthe third upstream RF receive signal RU3 to provide a third filtered RFreceive signal RF3 to the RF receive circuitry 62, which processes thethird filtered RF receive signal RF3 to provide the third receive signalRX3 to the RF system control circuitry 56.

In one embodiment of the RF communications circuitry 54, the fifthtunable RF filter path 122 is a third RF transmit filter, such that theRF system control circuitry 56 provides a third transmit signal TX3 tothe RF transmit circuitry 64, which processes the third transmit signalTX3 to provide a third upstream RF transmit signal TU3 to the fifthtunable RF filter path 122. The fifth tunable RF filter path 122receives and filters the third upstream RF transmit signal TU3 toprovide a third filtered RF transmit signal TF3, which is transmittedvia the first common connection node 74 by the first RF antenna 16.

In one embodiment of the RF communications circuitry 54, the firsttunable RF filter path 66, the second tunable RF filter path 68, thethird tunable RF filter path 110, the fourth tunable RF filter path 112,the fifth tunable RF filter path 122, and the sixth tunable RF filterpath 124 do not significantly load one another at frequencies ofinterest. Therefore, antenna switching circuitry 34, 42 (FIG. 3) may beavoided. As such, by directly coupling the first tunable RF filter path66, the second tunable RF filter path 68, the third tunable RF filterpath 110, the fourth tunable RF filter path 112, the fifth tunable RFfilter path 122 and the sixth tunable RF filter path 124 to the firstcommon connection node 74; front-end RF switching elements may beavoided, thereby reducing cost, size, and non-linearity; and increasingefficiency and flexibility of the RF communications circuitry 54.

In one embodiment of the RF communications circuitry 54, the RFcommunications circuitry 54 is an FDD communications system, such thateach of the first tunable RF filter path 66, the second tunable RFfilter path 68, the third tunable RF filter path 110, the fourth tunableRF filter path 112, the fifth tunable RF filter path 122, and the sixthtunable RF filter path 124 is a bandpass filter having a unique centerfrequency. As such, in one embodiment of the RF system control circuitry56, the first filter parameter of each of the first tunable RF filterpath 66, the second tunable RF filter path 68, the third tunable RFfilter path 110, the fourth tunable RF filter path 112, the fifthtunable RF filter path 122, and the sixth tunable RF filter path 124 isa unique center frequency.

FIG. 15 shows the RF communications circuitry 54 according to a furtherembodiment of the RF communications circuitry 54. The RF communicationscircuitry 54 illustrated in FIG. 15 is similar to the RF communicationscircuitry 54 illustrated in FIG. 4, except in the RF communicationscircuitry 54 illustrated in FIG. 15, the RF front-end circuitry 58further includes an RF antenna switch 130 and the third connection node114. Additionally, the first RF filter structure 60 further includes thethird tunable RF filter path 110. Instead of the first RF antenna 16being directly coupled to the first common connection node 74, asillustrated in FIG. 4, the RF antenna switch 130 is coupled between thefirst RF antenna 16 and the first common connection node 74. As such,the first common connection node 74 is coupled to the first RF antenna16 via the RF antenna switch 130. In this regard, the RF communicationscircuitry 54 is a hybrid RF communications system.

The RF antenna switch 130 has an antenna switch common connection node132, an antenna switch first connection node 134, an antenna switchsecond connection node 136, and an antenna switch third connection node138. The antenna switch common connection node 132 is coupled to thefirst RF antenna 16. In one embodiment of the RF antenna switch 130, theantenna switch common connection node 132 is directly coupled to thefirst RF antenna 16. The antenna switch first connection node 134 iscoupled to the first common connection node 74. In one embodiment of theRF antenna switch 130, the antenna switch first connection node 134 isdirectly coupled to the first common connection node 74. The antennaswitch second connection node 136 may be coupled to other circuitry (notshown). The antenna switch third connection node 138 may be coupled toother circuitry (not shown). In another embodiment of the RF antennaswitch 130, the antenna switch third connection node 138 is omitted. Ina further embodiment of the RF antenna switch 130, the RF antenna switch130 has at least one additional connection node.

The RF system control circuitry 56 provides a switch control signal SCSto the RF antenna switch 130. As such, the RF system control circuitry56 selects one of the antenna switch first connection node 134, theantenna switch second connection node 136, and the antenna switch thirdconnection node 138 to be coupled to the antenna switch commonconnection node 132 using the switch control signal SCS.

The third tunable RF filter path 110 is directly coupled between thefirst common connection node 74 and the third connection node 114. Inone embodiment of the RF communications circuitry 54, the third tunableRF filter path 110 is a second RF receive filter, such that the first RFantenna 16 forwards a received RF signal via the RF antenna switch 130and the first common connection node 74 to provide the second upstreamRF receive signal RU2 to the third tunable RF filter path 110, whichreceives and filters the second upstream RF receive signal RU2 toprovide the second filtered RF receive signal RF2 to the RF receivecircuitry 62. The RF receive circuitry 62 processes the second filteredRF receive signal RF2 to provide a second receive signal RX2 to the RFsystem control circuitry 56.

The RF system control circuitry 56 further provides the third filtercontrol signal FCS3. As such, in one embodiment of the RF communicationscircuitry 54, the RF system control circuitry 56 tunes a first filterparameter of the third tunable RF filter path 110 using the third filtercontrol signal FCS3. In one embodiment of the RF communicationscircuitry 54, the RF communications circuitry 54 uses the second tunableRF filter path 68 and the third tunable RF filter path 110 to providereceive CA. In an alternate embodiment of the RF communicationscircuitry 54, tunable RF filters allow for sharing a signal path toprovide both an FDD signal path and a TDD signal path, thereby loweringfront-end complexity.

FIG. 16 shows the RF communications circuitry 54 according to oneembodiment of the RF communications circuitry 54. The RF communicationscircuitry 54 illustrated in FIG. 16 is similar to the RF communicationscircuitry 54 illustrated in FIG. 15, except in the RF communicationscircuitry 54 illustrated in FIG. 16, the third tunable RF filter path110 is omitted. Additionally, in one embodiment of the RF communicationscircuitry 54, the RF receive circuitry 62, the RF transmit circuitry 64,and the first RF filter structure 60 are all broadband devices. As such,the RF communications circuitry 54 is broadband circuitry capable ofprocessing RF signals having wide frequency ranges.

FIG. 17 shows the RF communications circuitry 54 according to analternate embodiment of the RF communications circuitry 54. The RFcommunications circuitry 54 illustrated in FIG. 17 is similar to the RFcommunications circuitry 54 illustrated in FIG. 16, except in the RFcommunications circuitry 54 illustrated in FIG. 17, the RF receivecircuitry 62 is omitted and the RF front-end circuitry 58 furtherincludes a first RF front-end circuit 140, a second RF front-end circuit142, and a third RF front-end circuit 144.

The first RF front-end circuit 140 includes the RF transmit circuitry64. The second RF front-end circuit 142 includes the first RF filterstructure 60, the first connection node 70, the second connection node72, and the first common connection node 74. The third RF front-endcircuit 144 includes the RF antenna switch 130. In one embodiment of thefirst RF front-end circuit 140, the first RF front-end circuit 140 is afirst RF front-end integrated circuit (IC). In one embodiment of thesecond RF front-end circuit 142, the second RF front-end circuit 142 isa second RF front-end IC. In one embodiment of the third RF front-endcircuit 144, the third RF front-end circuit 144 is a third RF front-endIC.

FIG. 18 shows the RF communications circuitry 54 according to anadditional embodiment of the RF communications circuitry 54. The RFcommunications circuitry 54 illustrated in FIG. 18 is similar to the RFcommunications circuitry 54 illustrated in FIG. 16, except in the RFcommunications circuitry 54 illustrated in FIG. 18, the RF receivecircuitry 62 is omitted and the RF front-end circuitry 58 furtherincludes the first RF front-end circuit 140 and the second RF front-endcircuit 142.

The first RF front-end circuit 140 includes the RF transmit circuitry64. The second RF front-end circuit 142 includes the first RF filterstructure 60, the RF antenna switch 130, the first connection node 70,the second connection node 72, and the first common connection node 74.In one embodiment of the first RF front-end circuit 140, the first RFfront-end circuit 140 is the first RF front-end IC. In one embodiment ofthe second RF front-end circuit 142, the second RF front-end circuit 142is the second RF front-end IC.

FIG. 19 shows the RF communications circuitry 54 according to anotherembodiment of the RF communications circuitry 54. The RF communicationscircuitry 54 illustrated in FIG. 19 is similar to the RF communicationscircuitry 54 illustrated in FIG. 16, except in the RF communicationscircuitry 54 illustrated in FIG. 19, the RF receive circuitry 62 isomitted and the RF front-end circuitry 58 further includes the first RFfront-end circuit 140.

The first RF front-end circuit 140 includes the RF transmit circuitry64, the first RF filter structure 60, the RF antenna switch 130, thefirst connection node 70, the second connection node 72, and the firstcommon connection node 74. In one embodiment of the first RF front-endcircuit 140, the first RF front-end circuit 140 is the first RFfront-end IC.

FIG. 20 shows the RF communications circuitry 54 according to a furtherembodiment of the RF communications circuitry 54. The RF communicationscircuitry 54 illustrated in FIG. 20 is a TDD system, which is capable oftransmitting and receiving RF signals, but not simultaneously. As such,the RF communications circuitry 54 illustrated in FIG. 20 is similar tothe RF communications circuitry 54 illustrated in FIG. 4, except in theRF communications circuitry 54 illustrated in FIG. 20, the secondtunable RF filter path 68 and the second connection node 72 are omitted,and the RF front-end circuitry 58 further includes an RFtransmit/receive switch 146 coupled between the first tunable RF filterpath 66 and the RF receive circuitry 62, and further coupled between thefirst tunable RF filter path 66 and the RF transmit circuitry 64.

Since the RF communications circuitry 54 does not simultaneouslytransmit and receive RF signals, the first tunable RF filter path 66provides front-end transmit filtering when the RF communicationscircuitry 54 is transmitting RF signals and the first tunable RF filterpath 66 provides front-end receive filtering when the RF communicationscircuitry 54 is receiving RF signals. In this regard, the first tunableRF filter path 66 processes half-duplex signals.

The RF transmit/receive switch 146 has a transmit/receive switch commonconnection node 148, a transmit/receive switch first connection node150, and a transmit/receive switch second connection node 152. The RFreceive circuitry 62 is coupled between the RF system control circuitry56 and the transmit/receive switch second connection node 152. The RFtransmit circuitry 64 is coupled between the RF system control circuitry56 and the transmit/receive switch first connection node 150. The firstconnection node 70 is coupled to the transmit/receive switch commonconnection node 148.

The RF system control circuitry 56 provides a switch control signal SCSto the RF transmit/receive switch 146. As such, the RF system controlcircuitry 56 selects either the transmit/receive switch first connectionnode 150 or the transmit/receive switch second connection node 152 to becoupled to the transmit/receive switch common connection node 148 usingthe switch control signal SCS. Therefore, when the RF communicationscircuitry 54 is transmitting RF signals, the RF transmit circuitry 64 iscoupled to the first tunable RF filter path 66 and the RF receivecircuitry 62 is not coupled to the first tunable RF filter path 66.Conversely, when the RF communications circuitry 54 is receiving RFsignals, the RF receive circuitry 62 is coupled to the first tunable RFfilter path 66 and the RF transmit circuitry 64 is not coupled to thefirst tunable RF filter path 66.

FIG. 21 illustrates an exemplary embodiment of the first RF filterstructure 60. The first RF filter structure 60 includes a plurality ofresonators (referred to generically as elements R and specifically aselements R(i,j), where an integer i indicates a row position and aninteger j indicates a column position, where 1≦i≦M, 1≦j≦N and M is anyinteger greater than 1 and N is any integer greater than to 1. It shouldbe noted that in alternative embodiments the number of resonators R ineach row and column may be the same or different). The first tunable RFfilter path 66 includes row 1 of weakly coupled resonators R(1,1),R(1,2) through (R(1,N). All of the weakly coupled resonators R(1,1),R(1,2) through (R(1,N) are weakly coupled to one another. Furthermore,the first tunable RF filter path 66 is electrically connected betweenterminal 200 and terminal 202. In this manner, the first tunable RFfilter path 66 is configured to receive RF signals and output filteredRF signals. The second tunable RF filter path 68 includes row M ofweakly coupled resonators R(M,1), R(M,2) through R(M,N). All of theweakly coupled resonators R(M,1), R(M,2) through R(M,N) are weaklycoupled to one another. Furthermore, the second tunable RF filter path68 is electrically connected between terminal 204 and terminal 206. Inthis manner, the second tunable RF filter path 68 is configured toreceive RF signals and output filtered RF signals. It should be notedthat the first RF filter structure 60 may include any number of tunableRF filter paths, such as, for example, the third tunable RF filter path110, the fourth tunable RF filter path 112, the fifth tunable RF filterpath 122, and the sixth tunable RF filter path 124, described above withrespect to FIGS. 11-14. Each of the resonators R may be a tunableresonator, which allows for a resonant frequency of each of theresonators R to be varied to along a frequency range. In someembodiments, not all of the couplings between the resonators R are weak.A hybrid architecture having at least one pair of weakly coupledresonators R and strongly or moderately coupled resonators R is alsopossible.

Cross-coupling capacitive structures C are electrically connected to andbetween the resonators R. In this embodiment, each of the cross-couplingcapacitive structures C is a variable cross-coupling capacitivestructure, such as a varactor or an array of capacitors. To beindependent, the magnetic couplings may be negligible. Alternatively,the cross-coupling capacitive structures C may simply be provided by acapacitor with a fixed capacitance. With regard to the exemplaryembodiment shown in FIG. 21, the tunable RF filter paths of the first RFfilter structure 60 are independent of one another. As such, the firsttunable RF filter path 66 and the second tunable RF filter path 68 areindependent of one another and thus do not have cross-couplingcapacitive structures C between their resonators. Thus, in thisembodiment, the cross-coupling capacitive structures C do not connectany of the weakly coupled resonators R(1,1), R(1,2) through (R(1,N) toany of the weakly coupled resonators R(M,1), R(M,2) through (R(M,N).This provides increased isolation between the first tunable RF filterpath 66 and the second tunable RF filter path 68. In general, energytransfer between two weakly coupled resonators R in the first tunable RFfilter path 66 and the second tunable RF filter path 68 may be providedby multiple energy transfer components. For example, energy may betransferred between the resonators R only through mutual magneticcoupling, only through mutual electric coupling, or through both mutualelectric coupling and mutual magnetic coupling. Ideally, all of themutual coupling coefficients are provided as designed, but in practice,the mutual coupling coefficients also be the result of parasitics. Theinductors of the resonators R may also have magnetic coupling betweenthem. A total coupling between the resonators R is given by the sum ofmagnetic and electric coupling.

In order to provide the transfer functions of the tunable RF filterpaths 66, 68 with high out-of-band attenuation and a relatively lowfilter order, the tunable RF filter paths 66, 68 are configured toadjust notches in the transfer function, which are provided by theresonators R within the tunable RF filter paths 66, 68. The notches canbe provided using parallel tanks connected in series or in shunt along asignal path of the first tunable RF filter path 66. To provide thenotches, the parallel tanks operate approximately as an open circuit oras short circuits at certain frequencies. The notches can also beprovided using multi-signal path cancellation. In this case, the tunableRF filter paths 66, 68 may be smaller and/or have fewer inductors. Totune the total mutual coupling coefficients between the resonators Rtowards a desired value, the tunable RF filter paths 66, 68 areconfigured to vary variable electric coupling coefficients so thatparasitic couplings between the resonators R in the tunable RF filterpaths 66, 68 are absorbed into a desired frequency transfer function.

FIG. 22 illustrates an exemplary embodiment of the first tunable RFfilter path 66 in the first RF filter structure 60 shown in FIG. 21.While the exemplary embodiment shown in FIG. 22 is of the first tunableRF filter path 66, any of the tunable RF filter paths shown in the firstRF filter structure 60 of FIG. 21 may be arranged in accordance with theexemplary embodiment shown in FIG. 22. The first tunable RF filter path66 shown in FIG. 22 includes an embodiment of the resonator R(1,1) andan embodiment of the resonator R(1,2). The resonator R(1,1) and theresonator R(1,2) are weakly coupled to one another. More specifically,the resonator R(1,1) includes an inductor 208 and a capacitive structure210. The resonator R(1,2) includes an inductor 212, a capacitivestructure 214, and a capacitive structure 216.

The resonator R(1,1) and the resonator R(1,2) are a pair of weaklycoupled resonators. The resonator R(1,1) and the resonator R(1,2) areweakly coupled by providing the inductor 208 and the inductor 212 suchthat the inductor 208 and the inductor 212 are weakly magneticallycoupled. Although the resonator R(1,1) and the resonator R(1,2) areweakly coupled, the inductor 212 has a maximum lateral width and adisplacement between the inductor 208 and the inductor 212 is less thanor equal to half the maximum lateral width of the inductor 212. As such,the inductor 208 and the inductor 212 are relatively close to oneanother. The displacement between the inductor 208 and the inductor 212may be measured from a geometric centroid of the inductor 208 to ageometric centroid of the inductor 212. The maximum lateral width may bea maximum dimension of the inductor 212 along a plane defined by itslargest winding. The weak coupling between the inductor 208 and theinductor 212 is obtained through topological techniques. For example,the inductor 208 and the inductor 212 may be fully or partially aligned,where winding(s) of the inductor 208 and winding(s) of the inductor 212are configured to provide weak coupling through cancellation.Alternatively or additionally, a plane defining an orientation of thewinding(s) of the inductor 208 and a plane defining an orientation ofthe winding(s) of the inductor 212 may be fully or partially orthogonalto one another. Some of the magnetic couplings between the resonators Rcan be unidirectional (passive or active). This can significantlyimprove isolation (e.g., transmit and receive isolation in duplexers).

To maximize the quality (Q) factor of the tunable RF filter paths 66through 68, most of the total mutual coupling should be realizedmagnetically, and only fine-tuning is provided electrically. This alsohelps to reduce common-mode signal transfer in the differentialresonators and thus keeps the Q factor high. While the magnetic couplingcan be adjusted only statically, with a new layout design, the electriccoupling can be tuned on the fly (after fabrication). The filtercharacteristics (e.g., bias network structure, resonator capacitance)can be adjusted based on given coupling coefficients to maximize filterperformance.

To provide a tuning range to tune a transfer function of the firsttunable RF filter path 66 and provide a fast roll-off from alow-frequency side to a high-frequency side of the transfer function,the first tunable RF filter path 66 is configured to change a sign of atotal mutual coupling coefficient between the resonator R(1,1) and theresonator R(1,2). Accordingly, the first tunable RF filter path 66includes a cross-coupling capacitive structure C(P1) and across-coupling capacitive structure C(N1). The cross-coupling capacitivestructure C(P1) and the cross-coupling capacitive structure C(N1) areembodiments of the cross-coupling capacitive structures C describedabove with regard to FIG. 21. As shown in FIG. 22, the cross-couplingcapacitive structure C(P1) is electrically connected between theresonator R(1,1) and the resonator R(1,2) so as to provide a positivecoupling coefficient between the resonator R(1,1) and the resonatorR(1,2). The cross-coupling capacitive structure C(P1) is a variablecross-coupling capacitive structure configured to vary the positivecoupling coefficient provided between the resonator R(1,1) and theresonator R(1,2). The cross-coupling capacitive structure C(N1) iselectrically connected between the resonator R(1,1) and the resonatorR(1,2) so as to provide a negative coupling coefficient between theresonator R(1,1) and the resonator R(1,2). The cross-coupling capacitivestructure C(N1) is a variable cross-coupling capacitive structureconfigured to vary the negative coupling coefficient provided betweenthe resonator R(1,1) and the resonator R(1,2). The arrangement of thecross-coupling capacitive structure C(P1) and the cross-couplingcapacitive structure C(N1) shown in FIG. 22 is a V-bridge structure. Inalternative embodiments, some or all of the cross-coupling capacitivestructures is fixed (not variable).

In the resonator R(1,1), the inductor 208 and the capacitive structure210 are electrically connected in parallel. More specifically, theinductor 208 has an end 217 and an end 218, which are disposed oppositeto one another. The ends 217, 218 are each electrically connected to thecapacitive structure 210, which is grounded. Thus, the resonator R(1,1)is a single-ended resonator. On the other hand, the inductor 212 iselectrically connected between the capacitive structure 214 and thecapacitive structure 216. More specifically, the inductor 212 has an end220 and an end 222, which are disposed opposite to one another. The end220 is electrically connected to the capacitive structure 214 and theend 222 is electrically connected to the capacitive structure 216. Boththe capacitive structure 214 and the capacitive structure 216 aregrounded. Thus, the resonator R(1,2) is a differential resonator. In analternative, an inductor with a center tap can be used. The tap can beconnected to ground and only a single capacitive structure can be used.In yet another embodiment, both an inductor and a capacitive structuremay have a center tap that is grounded. In still another embodiment,neither the inductor nor the capacitive structure may have a groundedcenter tap.

The inductor 208 is magnetically coupled to the inductor 212 such thatan RF signal received at the end 217 of the inductor 208 with a voltagepolarity (i.e., either a positive voltage polarity or a negative voltagepolarity) results in a filtered RF signal being transmitted out the end220 of the inductor 212 with the same voltage polarity. Also, theinductor 212 is magnetically coupled to the inductor 208 such that an RFsignal received at the end 220 of the inductor 212 with a voltagepolarity (i.e., either a positive voltage polarity or a negative voltagepolarity) results in a filtered RF signal being transmitted out the end217 of the inductor 208 with the same voltage polarity. This isindicated in FIG. 22 by the dot convention where a dot is placed at theend 217 of the inductor 208 and a dot is placed at the end 220 of theinductor 212. By using two independent and adjustable couplingcoefficients (i.e., the positive coupling coefficient and the negativecoupling coefficient) with the resonator R(1,2) (i.e., the differentialresonator), the transfer function of the first tunable RF filter path 66is provided so as to be fully adjustable. More specifically, theinductors 208, 212 may be magnetically coupled so as to have a lowmagnetic coupling coefficient through field cancellation, with thevariable positive coupling coefficient and the variable negativecoupling coefficient. In this case, the inductor 208 and the inductor212 are arranged such that a mutual magnetic coupling between theinductor 208 and the inductor 212 cancel. Alternatively, the inductor208 and the inductor 212 are arranged such that the inductor 212 reducesa mutual magnetic coupling coefficient of the inductor 208. With respectto the magnetic coupling coefficient, the variable positive couplingcoefficient is a variable positive electric coupling coefficient and thevariable negative coupling coefficient is a variable negative electriccoupling coefficient. The variable positive electric couplingcoefficient and the variable negative electric coupling coefficientoppose each other to create a tunable filter characteristic.

The resonator R(1,2) is operably associated with the resonator R(1,1)such that an energy transfer factor between the resonator R(1,1) and theresonator R(1,2) is less than 10%. A total mutual coupling between theresonator R(1,1) and the resonator R(1,2) is provided by a sum total ofthe mutual magnetic factor between the resonator R(1,1) and theresonator R(1,2) and the mutual electric coupling coefficients betweenthe resonator R(1,1) and the resonator R(1,2). In this embodiment, themutual magnetic coupling coefficient between the inductor 208 and theinductor 212 is a fixed mutual magnetic coupling coefficient. Althoughembodiments of the resonators R(1,1), R(1,2) may be provided so as toprovide a variable magnetic coupling coefficient between the resonatorsR(1,1), R(1,2), embodiments of the resonators R(1,1), R(1,2) thatprovide variable magnetic couplings can be costly and difficult torealize. However, providing variable electric coupling coefficients(i.e., the variable positive electric coupling coefficient and thevariable electric negative coupling coefficient) is easier and moreeconomical. Thus, using the cross-coupling capacitive structure C(P1)and the cross-coupling capacitive structure C(N1) to provide thevariable positive electric coupling coefficient and the variableelectric negative coupling coefficient is an economical technique forproviding a tunable filter characteristic between the resonators R(1,1),R(1,2). Furthermore, since the mutual magnetic coupling coefficientbetween the inductor 208 and the inductor 212 is fixed, the firsttunable RF filter path 66 has lower insertion losses.

In the embodiment shown in FIG. 22, the inductor 208 and the 212inductor are the same size. Alternatively, the inductor 208 and theinductor 212 may be different sizes. For example, the inductor 212 maybe smaller than the inductor 208. By determining a distance between theinductor 208 and the inductor 212, the magnetic coupling coefficientbetween the inductor 208 and the inductor 212 can be set. With regard tothe inductors 208, 212 shown in FIG. 22, the inductor 208 may be afolded inductor configured to generate a first confined magnetic field,while the inductor 212 may be a folded inductor configured to generate asecond confined magnetic field. Magnetic field lines of the firstconfined magnetic field and of the second confined magnetic field thatare external to the inductor 208 and inductor 212 are cancelled byopposing magnetic field lines in all directions. When the inductor 208and the inductor 212 are folded inductors, the folded inductors can bestacked. This allows building the first tunable RF filter path 66 suchthat several inductors 208, 212 are stacked. Furthermore, thisarrangement allows for a specially sized interconnect structure thatelectrically connects the inductors 208, 212 to the capacitive structure210, the capacitive structure 214, the capacitive structure 216, thecross-coupling capacitive structure C(P1), and the cross-couplingcapacitive structure C(N1). The specially sized interconnect increasesthe Q factor of the capacitive structure 210, the capacitive structure214, the capacitive structure 216, the cross-coupling capacitivestructure C(P1), and the cross-coupling capacitive structure C(N1), andallows for precise control of their variable capacitances. Weaklycoupled filters can also be realized with planar field cancellationstructures.

FIG. 23 illustrates an exemplary embodiment of the first tunable RFfilter path 66 in the first RF filter structure 60 shown in FIG. 21.While the exemplary embodiment shown in FIG. 23 is of the first tunableRF filter path 66, any of the tunable RF filter paths shown in the firstRF filter structure 60 of FIG. 21 may be arranged in accordance with theexemplary embodiment shown in FIG. 23. The first tunable RF filter path66 shown in FIG. 23 includes an embodiment of the resonator R(1,1) andan embodiment of the resonator R(1,2). The resonator R(1,1) and theresonator R(1,2) are weakly coupled to one another. The embodiment ofthe resonator R(1,2) is the same as the embodiment of the resonatorR(1,2) shown in FIG. 22. Thus, the resonator R(1,2) shown in FIG. 23 isa differential resonator that includes the inductor 212, the capacitivestructure 214, and the capacitive structure 216. Additionally, like theembodiment of the resonator R(1,1) shown in FIG. 22, the embodiment ofthe resonator R(1,1) shown in FIG. 23 includes the inductor 208 and thecapacitive structure 210. However, in this embodiment, the resonatorR(1,1) shown in FIG. 23 is a differential resonator and further includesa capacitive structure 224. More specifically, the end 217 of theinductor 208 is electrically connected to the capacitive structure 210and the end 218 of the inductor 208 is electrically connected to thecapacitive structure 224. Both the capacitive structure 210 and thecapacitive structure 224 are grounded. Like the capacitive structure210, the capacitive structure 224 is also a variable capacitivestructure, such as a programmable array of capacitors or a varactor.Alternatively, a center tap of an inductor may be grounded. In yetanother embodiment, the inductor and a capacitive structure may be RFfloating (a low-resistance connection to ground).

The resonator R(1,1) and the resonator R(1,2) are a pair of weaklycoupled resonators. Like the first tunable RF filter path 66 shown inFIG. 22, the resonator R(1,1) and the resonator R(1,2) are weaklycoupled by providing the inductor 208 and the inductor 212 such that theinductor 208 and the inductor 212 are weakly coupled. Thus, the inductor208 and the inductor 212 may have a magnetic coupling coefficient thatis less than or equal to approximately 0.3. Although the resonatorR(1,1) and the resonator R(1,2) are weakly coupled, a displacementbetween the inductor 208 and the inductor 212 is less than or equal tohalf the maximum lateral width of the inductor 212. As such, theinductor 208 and the inductor 212 are relatively close to one another.The displacement between the inductor 208 and the inductor 212 may bemeasured from a geometric centroid of the inductor 208 to a geometriccentroid of the inductor 212. The maximum lateral width may be a maximumdimension of the inductor 212 along a plane defined by its largestwinding.

The weak coupling between the inductor 208 and the inductor 212 isobtained through topological techniques. For example, the inductor 208and the inductor 212 may be fully or partially aligned, where winding(s)of the inductor 208 and winding(s) of the inductor 212 are configured toprovide weak coupling through cancellation. Alternatively oradditionally, a plane defining an orientation of the windings of theinductor 208 and a plane defining an orientation of the windings of theinductor 212 may be fully or partially orthogonal to one another.

The resonator R(1,2) is operably associated with the resonator R(1,1)such that an energy transfer factor between the resonator R(1,1) and theresonator R(1,2) is less than 10%. To provide a tuning range to tune atransfer function of the first tunable RF filter path 66 such to providea fast roll-off from a low-frequency side to a high-frequency siderequires changing a sign of the total mutual coupling coefficientbetween the resonator R(1,1) and the resonator R(1,2). Like theembodiment of the first tunable RF filter path 66 shown in FIG. 22, thefirst tunable RF filter path 66 shown in FIG. 23 includes thecross-coupling capacitive structure C(P1) and the cross-couplingcapacitive structure C(N1). The cross-coupling capacitive structureC(P1) and the cross-coupling capacitive structure C(N1) are arranged inthe same manner described above with respect to FIG. 22. However, inthis embodiment, the first tunable RF filter path 66 shown in FIG. 23also includes a cross-coupling capacitive structure C(P2) and across-coupling capacitive structure C(N2). The cross-coupling capacitivestructure C(P2) and the cross-coupling capacitive structure C(N2) arealso embodiments of the cross-coupling capacitive structures C describedabove with regard to FIG. 21.

As described above with respect to FIG. 22, the cross-couplingcapacitive structure C(P1) is electrically connected between theresonator R(1,1) and the resonator R(1,2) so as to provide the positivecoupling coefficient (i.e., the variable positive electric couplingcoefficient) between the resonator R(1,1) and the resonator R(1,2). Alsoas described above with respect to FIG. 22, the cross-couplingcapacitive structure C(N1) is electrically connected between theresonator R(1,1) and the resonator R(1,2) so as to provide the negativecoupling coefficient (i.e., the variable negative electric couplingcoefficient) between the resonator R(1,1) and the resonator R(1,2). Withregard to the cross-coupling capacitive structure C(P2), thecross-coupling capacitive structure C(P2) is electrically connectedbetween the resonator R(1,1) and the resonator R(1,2) so as to provideanother positive coupling coefficient (i.e., another variable positiveelectric coupling coefficient) between the resonator R(1,1) and theresonator R(1,2). In this embodiment, the cross-coupling capacitivestructure C(P2) is electrically connected between the end 218 of theinductor 208 and the end 222 of the inductor 212. The cross-couplingcapacitive structure C(P2) is a variable cross-coupling capacitivestructure configured to vary the other positive coupling coefficient(i.e., the other variable positive electric coupling coefficient)provided between the resonator R(1,1) and the resonator R(1,2). Withregard to the cross-coupling capacitive structure C(N2), thecross-coupling capacitive structure C(N2) is electrically connectedbetween the resonator R(1,1) and the resonator R(1,2) so as to provideanother negative coupling coefficient (i.e., another variable negativeelectric coupling coefficient) between the resonator R(1,1) and theresonator R(1,2). In this embodiment, the cross-coupling capacitivestructure C(N2) is electrically connected between the end 218 of theinductor 208 and the end 220 of the inductor 212. The cross-couplingcapacitive structure C(N2) is a variable cross-coupling capacitivestructure configured to vary the negative coupling coefficient (i.e.,the other variable negative electric coupling coefficient) providedbetween the resonator R(1,1) and the resonator R(1,2). The arrangementof the cross-coupling capacitive structure C(P1), the cross-couplingcapacitive structure C(N1), the cross-coupling capacitive structureC(P2), and the cross-coupling capacitive structure C(N2) shown in FIG.23 is an X-bridge structure.

As shown in FIG. 23, the resonator R(1,2) is operably associated withthe resonator R(1,1) such that an energy transfer factor between theresonator R(1,1) and the resonator R(1,2) is less than 10%. The totalmutual coupling between the resonator R(1,1) and the resonator R(1,2) isprovided by a sum total of the mutual magnetic factor between theresonator R(1,1) and the resonator R(1,2) and the mutual electriccoupling coefficients between the resonator R(1,1) and the resonatorR(1,2). Thus, in this embodiment, the total mutual coupling between theresonator R(1,1) and the resonator R(1,2) is provided by the sum totalof the mutual magnetic coupling coefficient, the variable positiveelectric coupling coefficient provided by the cross-coupling capacitivestructure C(P1), the variable negative electric coupling coefficientprovided by the cross-coupling capacitive structure C(N1), the othervariable positive electric coupling coefficient provided by thecross-coupling capacitive structure C(P2), and the other variablenegative electric coupling coefficient provided by the cross-couplingcapacitive structure C(N2).

FIG. 24 illustrates an exemplary embodiment of the first tunable RFfilter path 66 in the first RF filter structure 60 shown in FIG. 21.While the exemplary embodiment shown in FIG. 24 is of the first tunableRF filter path 66, any of the tunable RF filter paths shown in the firstRF filter structure 60 of FIG. 21 may be arranged in accordance with theexemplary embodiment shown in FIG. 24. The first tunable RF filter path66 shown in FIG. 24 includes an embodiment of the resonator R(1,1) andan embodiment of the resonator R(1,2). The resonator R(1,1) and theresonator R(1,2) are weakly coupled to one another. The embodiment ofthe resonator R(1,1) is the same as the embodiment of the resonatorR(1,1) shown in FIG. 22. Thus, the resonator R(1,1) shown in FIG. 24 isa single-ended resonator that includes the inductor 208 and thecapacitive structure 210. Additionally, like the embodiment of theresonator R(1,2) shown in FIG. 22, the embodiment of the resonatorR(1,2) shown in FIG. 24 includes the inductor 212 and the capacitivestructure 214. However, in this embodiment, the resonator R(1,2) shownin FIG. 24 is a single-ended resonator. More specifically, the end 220and the end 222 of the inductor 212 are each electrically connected tothe capacitive structure 214, which is grounded.

The resonator R(1,1) and the resonator R(1,2) are a pair of weaklycoupled resonators. Like the first tunable RF filter path 66 shown inFIG. 22, the resonator R(1,1) and the resonator R(1,2) are weaklycoupled by providing the inductor 208 and the inductor 212 such that theinductor 208 and the inductor 212 are weakly coupled. Thus, the inductor208 and the inductor 212 may have a magnetic coupling coefficient thatis less than or equal to approximately 0.3. Although the resonatorR(1,1) and the resonator R(1,2) are weakly coupled, the displacementbetween the inductor 208 and the inductor 212 is less than or equal tohalf the maximum lateral width of the inductor 212. As such, theinductor 208 and the inductor 212 are relatively close to one another.The displacement between the inductor 208 and the inductor 212 may bemeasured from the geometric centroid of the inductor 208 to thegeometric centroid of the inductor 212. The maximum lateral width may bea maximum dimension of the inductor 212 along a plane defined by itslargest winding. The weak coupling between the inductor 208 and theinductor 212 is obtained through topological techniques. For example,the inductor 208 and the inductor 212 may be fully or partially aligned,where winding(s) of the inductor 208 and winding(s) of the inductor 212are configured to provide weak coupling through cancellation.Alternatively or additionally, a plane defining an orientation of thewindings of the inductor 208 and a plane defining an orientation of thewindings of the inductor 212 may be fully or partially orthogonal to oneanother.

The resonator R(1,2) is operably associated with the resonator R(1,1)such that an energy transfer factor between the resonator R(1,1) and theresonator R(1,2) is less than 10%. To provide a tuning range to tune atransfer function of the first tunable RF filter path 66 and provide afast roll-off from a low-frequency side to a high-frequency side of thetransfer function, the first tunable RF filter path 66 is configured tochange a sign of a total mutual coupling coefficient between theresonator R(1,1) and the resonator R(1,2). However, in this embodiment,the first tunable RF filter path 66 shown in FIG. 24 only includes thecross-coupling capacitive structure C(P1), which is electricallyconnected between the end 217 of the inductor 208 and the end 220 of theinductor 212. As discussed above with respect to FIGS. 22 and 23, thecross-coupling capacitive structure C(P1) is a variable cross-couplingcapacitive structure configured to vary the positive couplingcoefficient (i.e., the variable positive electric coupling coefficient)provided between the resonator R(1,1) and the resonator R(1,2). Thus, inorder to allow for the sign of the total mutual coupling coefficientbetween the resonator R(1,1) and the resonator R(1,2) to be changed, theinductor 208 and the inductor 212 are arranged so as to provide a fixednegative mutual magnetic coupling coefficient between the inductor 208of the resonator R(1,1) and the inductor 212 of the resonator R(1,2). Assuch, varying the variable positive electric coupling coefficient allowsfor the sign of the total mutual coupling coefficient between theresonator R(1,1) and the resonator R(1,2) to be changed using only thecross-coupling capacitive structure C(P1).

As such, in this embodiment, the inductor 208 is magnetically coupled tothe inductor 212 such that an RF signal received at the end 217 of theinductor 208 with a voltage polarity (i.e., either a positive voltagepolarity or a negative voltage polarity) results in a filtered RF signalwith the same voltage polarity being transmitted out the end 222 of theinductor 212. In addition, the inductor 212 is magnetically coupled tothe inductor 208 such that an RF signal received at the end 222 of theinductor 212 with a voltage polarity (i.e., either a positive voltagepolarity or a negative voltage polarity) results in a filtered RF signalwith the same voltage polarity being transmitted out the end 217 of theinductor 208. This is indicated in FIG. 24 by the dot convention where adot is placed at the end 217 of the inductor 208 and a dot is placed atthe end 222 of the inductor 212. By using the fixed negative mutualmagnetic coupling coefficient and the variable positive electriccoupling coefficient, the transfer function of the first tunable RFfilter path 66 is provided so to be fully adjustable. The arrangement ofthe cross-coupling capacitive structure C(P1) shown in FIG. 24 is asingle positive bridge structure.

FIG. 25 illustrates another exemplary embodiment of the first tunable RFfilter path 66 in the first RF filter structure 60 shown in FIG. 21.While the exemplary embodiment shown in FIG. 25 is of the first tunableRF filter path 66, any of the tunable RF filter paths shown in the firstRF filter structure 60 of FIG. 21 may be arranged in accordance with theexemplary embodiment shown in FIG. 25. The first tunable RF filter path66 shown in FIG. 25 includes an embodiment of the resonator R(1,1) andan embodiment of the resonator R(1,2). The resonator R(1,1) and theresonator R(1,2) are weakly coupled to one another. The embodiment ofthe resonator R(1,1) is the same as the embodiment of the resonatorR(1,1) shown in FIG. 22. Thus, the resonator R(1,1) shown in FIG. 25 isa single-ended resonator that includes the inductor 208 and thecapacitive structure 210, which are arranged in the same mannerdescribed above with respect to FIG. 22. Like the resonator R(1,2) shownin FIG. 24, the resonator R(1,2) shown in FIG. 25 is a single-endedresonator that includes the inductor 212 and the capacitive structure214. However, the inductor 208 shown in FIG. 25 is magnetically coupledto the inductor 212 such that an RF signal received at the end 217 ofthe inductor 208 with a voltage polarity (i.e., either a positivevoltage polarity or a negative voltage polarity) results in a filteredRF signal with the same voltage polarity being transmitted out the end220 of the inductor 212. Also, the inductor 212 shown in FIG. 25 ismagnetically coupled to the inductor 208 such that an RF signal receivedat the end 220 of the inductor 212 with a voltage polarity (i.e., eithera positive voltage polarity or a negative voltage polarity) results in afiltered RF signal with the same voltage polarity being transmitted outthe end 217 of the inductor 208. This is indicated in FIG. 25 by the dotconvention where a dot is placed at the end 217 of the inductor 208 anda dot is placed at the end 220 of the inductor 212. In alternativeembodiments, the resonator R(1,2) is a differential resonator. In yetanother alternative embodiment, the resonator R(1,1) is a single-endedresonator while the resonator R(1,2) is a differential resonator.

The resonator R(1,1) and the resonator R(1,2) are a pair of weaklycoupled resonators. Like the first tunable RF filter path 66 shown inFIG. 22, the resonator R(1,1) and the resonator R(1,2) are weaklycoupled by providing the inductor 208 and the inductor 212 such that theinductor 208 and the inductor 212 are weakly coupled. Thus, the inductor208 and the inductor 212 may have a fixed magnetic coupling coefficientthat is less than or equal to approximately 0.3. Although the resonatorR(1,1) and the resonator R(1,2) are weakly coupled, a displacementbetween the inductor 208 and the inductor 212 is less than or equal tohalf the maximum lateral width of the inductor 212. As such, theinductor 208 and the inductor 212 are relatively close to one another.The displacement between the inductor 208 and the inductor 212 may bemeasured from a geometric centroid of the inductor 208 to a geometriccentroid of the inductor 212. The maximum lateral width may be a maximumdimension of the inductor 212 along a plane defined by its largestwinding.

The weak coupling between the inductor 208 and the inductor 212 isobtained through topological techniques. For example, the inductor 208and the inductor 212 may be fully or partially aligned, where winding(s)of the inductor 208 and winding(s) of the inductor 212 are configured toprovide weak coupling through cancellation. Alternatively oradditionally, a plane defining an orientation of the windings of theinductor 208 and a plane defining an orientation of the windings of theinductor 212 may be fully or partially orthogonal to one another.

The resonator R(1,2) is operably associated with the resonator R(1,1)such that an energy transfer factor between the resonator R(1,1) and theresonator R(1,2) is less than 10%. To provide a tuning range to tune thetransfer function of the first tunable RF filter path 66 and to providea fast roll-off from the low-frequency side to the high-frequency sideof the transfer function, the first tunable RF filter path 66 isconfigured to change the sign of the total mutual coupling coefficientbetween the resonator R(1,1) and the resonator R(1,2). In thisembodiment, the first tunable RF filter path 66 shown in FIG. 25includes a cross-coupling capacitive structure C(PH1), a cross-couplingcapacitive structure (CNH1), a cross-coupling capacitive structureC(I1), a cross-coupling capacitive structure C(PH2), and across-coupling capacitive structure C(NH2). The cross-couplingcapacitive structure C(PH1), the cross-coupling capacitive structure(CNH1), the cross-coupling capacitive structure C(I1), thecross-coupling capacitive structure C(PH2), and the cross-couplingcapacitive structure C(NH2) are also embodiments of the cross-couplingcapacitive structures C described above with regard to FIG. 21.

The cross-coupling capacitive structure C(PH1) and the cross-couplingcapacitive structure C(NH1) are arranged to form a first capacitivevoltage divider. The first capacitive voltage divider is electricallyconnected to the resonator R(1,1). More specifically, the cross-couplingcapacitive structure C(PH1) is electrically connected between the end217 of the inductor 208 and a common connection node H1. Thecross-coupling capacitive structure C(NH1) is electrically connectedbetween the end 218 of the inductor 208 and the common connection nodeH1. Additionally, the cross-coupling capacitive structure C(PH2) and thecross-coupling capacitive structure C(NH2) are arranged to form a secondcapacitive voltage divider. The second capacitive voltage divider iselectrically connected to the resonator R(1,2). More specifically, thecross-coupling capacitive structure C(PH2) is electrically connectedbetween the end 220 of the inductor 212 and a common connection node H2.The cross-coupling capacitive structure C(NH2) is electrically connectedbetween the end 222 of the inductor 212 and the common connection nodeH2. As shown in FIG. 25, the cross-coupling capacitive structure C(I1)is electrically connected between the first capacitive voltage dividerand the second capacitive voltage divider. More specifically, thecross-coupling capacitive structure C(I1) is electrically connectedbetween the common connection node H1 and the common connection node H2.The arrangement of the cross-coupling capacitive structure C(PH1), thecross-coupling capacitive structure C(NH1), the cross-couplingcapacitive structure C(PH2), the cross-coupling capacitive structureC(NH2), and the cross-coupling capacitive structure C(I1) shown in FIG.25 is an H-bridge structure. In an alternative H-bridge structure, thecross-coupling capacitive structure C(I1) is not provided and insteadthere is a short between the common connection node H1 and the commonconnection node H2. In addition, a center tap of the inductor 208 may begrounded and/or the common connection node H1 may be grounded. Finally,a high impedance to ground may be provided at the common connection nodeH1.

With regard to the first capacitive voltage divider, the cross-couplingcapacitive structure C(PH1) is a variable cross-coupling capacitivestructure configured to vary a first variable positive electric couplingcoefficient provided between the resonator R(1,1) and the commonconnection node H1. The cross-coupling capacitive structure C(NH1) is avariable cross-coupling capacitive structure configured to vary a firstvariable negative electric coupling coefficient provided between theresonator R(1,1) and the common connection node H1. Thus, a mutualelectric coupling coefficient of the resonator R(1,1) is approximatelyequal to the first variable positive electric coupling coefficient andthe first variable negative electric coupling coefficient.

With regard to the second capacitive voltage divider, the cross-couplingcapacitive structure C(PH2) is a variable cross-coupling capacitivestructure configured to vary a second variable positive electriccoupling coefficient provided between the resonator R(1,2) and thecommon connection node H2. The cross-coupling capacitive structureC(NH2) is a variable cross-coupling capacitive structure configured tovary a second variable negative electric coupling coefficient providedbetween the resonator R(1,2) and the common connection node H2. Thus, amutual electric coupling coefficient of the resonator R(1,2) isapproximately equal to the second variable positive electric couplingcoefficient and the second variable negative electric couplingcoefficient. Furthermore, the cross-coupling capacitive structure C(I1)is a variable cross-coupling capacitive structure configured to vary afirst variable intermediate electric coupling coefficient providedbetween the common connection node H1 and the common connection node H2.The first tunable RF filter path 66 shown in FIG. 25 thus has a totalmutual coupling coefficient between the resonator R(1,1) and theresonator R(1,2) equal to the sum total of the mutual magnetic couplingcoefficient between the inductor 208 and the inductor 212, the mutualelectric coupling coefficient of the resonator R(1,1), the mutualelectric coupling coefficient of the resonator R(1,2), and the firstvariable intermediate electric coupling coefficient provided between thecommon connection node H1 and the common connection node H2. Inalternative embodiments, cross-coupling capacitive structures with fixedcapacitances are provided.

In one embodiment, the cross-coupling capacitive structure C(PH1), thecross-coupling capacitive structure C(NH1), the cross-couplingcapacitive structure C(PH2), the cross-coupling capacitive structureC(NH2), and the cross-coupling capacitive structure C(I1) may each beprovided as a varactor. However, the cross-coupling capacitive structureC(PH1), the cross-coupling capacitive structure C(NH1), thecross-coupling capacitive structure C(PH2), the cross-couplingcapacitive structure C(NH2), and the cross-coupling capacitive structureC(I1) may each be provided as a programmable array of capacitors inorder to reduce insertion losses and improve linearity. Thecross-coupling capacitive structure C(PH1), the cross-couplingcapacitive structure C(NH1), the cross-coupling capacitive structureC(PH2), the cross-coupling capacitive structure C(NH2), and thecross-coupling capacitive structure C(I1) can also be any combination ofsuitable variable cross-coupling capacitive structures, such ascombinations of varactors and programmable arrays of capacitors.Although the H-bridge structure can provide good linearity and lowinsertion losses, the H-bridge structure can also suffer fromcommon-mode signal transfer.

FIG. 26 illustrates yet another exemplary embodiment of the firsttunable RF filter path 66 in the first RF filter structure 60 shown inFIG. 21. While the exemplary embodiment shown in FIG. 26 is of the firsttunable RF filter path 66, any of the tunable RF filter paths shown inthe first RF filter structure 60 of FIG. 21 may be arranged inaccordance with the exemplary embodiment shown in FIG. 26. The firsttunable RF filter path 66 shown in FIG. 26 can be used to ameliorate thecommon-mode signal transfer of the H-bridge structure shown in FIG. 25.More specifically, the first tunable RF filter path 66 shown in FIG. 26includes the same embodiment of the resonator R(1,1) and the sameembodiment of the resonator R(1,2) described above with respect to FIG.25. Furthermore, the first tunable RF filter path 66 shown in FIG. 26includes the first capacitive voltage divider with the cross-couplingcapacitive structure C(PH1) and the cross-coupling capacitive structureC(NH1) described above with respect to FIG. 25, the second capacitivevoltage divider with the cross-coupling capacitive structure C(PH2) andthe cross-coupling capacitive structure (CNH2) described above withrespect to FIG. 25, and the cross-coupling capacitive structure C(I1)described above with respect to FIG. 25. However, in this embodiment,the first tunable RF filter path 66 shown in FIG. 26 also includes across-coupling capacitive structure C(PH3), a cross-coupling capacitivestructure (CNH3), a cross-coupling capacitive structure C(I2), across-coupling capacitive structure C(PH4), and a cross-couplingcapacitive structure C(NH4). The cross-coupling capacitive structureC(PH3), the cross-coupling capacitive structure (CNH3), thecross-coupling capacitive structure C(I2), the cross-coupling capacitivestructure C(PH4), and the cross-coupling capacitive structure C(NH4) arealso embodiments of the cross-coupling capacitive structures C describedabove with regard to FIG. 21.

As shown in FIG. 26, the cross-coupling capacitive structure C(PH3) andthe cross-coupling capacitive structure C(NH3) are arranged to form athird capacitive voltage divider. The third capacitive voltage divideris electrically connected to the resonator R(1,1). More specifically,the cross-coupling capacitive structure C(PH3) is electrically connectedbetween the end 217 of the inductor 208 and a common connection node H3.The cross-coupling capacitive structure C(NH3) is electrically connectedbetween the end 218 of the inductor 208 and the common connection nodeH3. Additionally, the cross-coupling capacitive structure C(PH4) and thecross-coupling capacitive structure C(NH4) are arranged to form a fourthcapacitive voltage divider. The fourth capacitive voltage divider iselectrically connected to the resonator R(1,2). More specifically, thecross-coupling capacitive structure C(PH4) is electrically connectedbetween the end 220 of the inductor 212 and a common connection node H4.The cross-coupling capacitive structure C(NH4) is electrically connectedbetween the end 222 of the inductor 212 and the common connection nodeH4. As shown in FIG. 26, the cross-coupling capacitive structure C(I2)is electrically connected between first capacitive voltage divider andthe second capacitive voltage divider. More specifically, thecross-coupling capacitive structure C(I2) is electrically connectedbetween the common connection node H3 and the common connection node H4.Alternatively, the cross-coupling capacitive structure C(I1) and thecross-coupling capacitive structure C(I2) can be replaced with shorts.The arrangement of the cross-coupling capacitive structure C(PH1), thecross-coupling capacitive structure C(NH1), the cross-couplingcapacitive structure C(PH2), the cross-coupling capacitive structureC(NH2), the cross-coupling capacitive structure C(I1), thecross-coupling capacitive structure C(PH3), the cross-couplingcapacitive structure C(NH3), the cross-coupling capacitive structureC(PH4), the cross-coupling capacitive structure C(NH4), and thecross-coupling capacitive structure C(I2) shown in FIG. 26 is a doubleH-bridge structure.

With regard to the third capacitive voltage divider, the cross-couplingcapacitive structure C(PH3) is a variable cross-coupling capacitivestructure configured to vary a third variable positive electric couplingcoefficient provided between the resonator R(1,1) and the commonconnection node H3. The cross-coupling capacitive structure C(NH3) is avariable cross-coupling capacitive structure configured to vary a thirdvariable negative electric coupling coefficient provided between theresonator R(1,1) and the common connection node H3. Thus, a mutualelectric coupling coefficient of the resonator R(1,1) is approximatelyequal to the first variable positive electric coupling coefficient, thethird variable positive electric coupling coefficient, the firstvariable negative electric coupling coefficient and the third variablenegative electric coupling coefficient.

With regard to the fourth capacitive voltage divider, the cross-couplingcapacitive structure C(PH4) is a variable cross-coupling capacitivestructure configured to vary a fourth variable positive electriccoupling coefficient provided between the resonator R(1,2) and thecommon connection node H4. The cross-coupling capacitive structureC(NH4) is a variable cross-coupling capacitive structure configured tovary a fourth variable negative electric coupling coefficient providedbetween the resonator R(1,2) and the common connection node H4. Thus, amutual electric coupling coefficient of the resonator R(1,2) isapproximately equal to the second variable positive electric couplingcoefficient, the fourth variable positive coupling coefficient, thesecond variable negative coupling coefficient, and the fourth variablenegative electric coupling coefficient. Furthermore, the cross-couplingcapacitive structure C(I2) is a variable cross-coupling capacitivestructure configured to vary a second variable intermediate electriccoupling coefficient provided between the common connection node H3 andthe common connection node H4. The first tunable RF filter path 66 shownin FIG. 26 thus has a total mutual coupling coefficient between theresonator R(1,1) and the resonator R(1,2) equal to the sum total of themutual magnetic coupling coefficient between the inductor 208 and theinductor 212, the mutual electric coupling coefficient of the resonatorR(1,1), the mutual electric coupling coefficient of the resonatorR(1,2), the first variable intermediate electric coupling coefficientprovided between the common connection node H1 and the common connectionnode H2 and the second variable intermediate electric couplingcoefficient provided between the common connection node H3 and thecommon connection node H4. The double H-bridge structure thus includestwo H-bridge structures. The two H-bridge structures allow forcommon-mode signal transfers of the two H-bridge structures to opposeone another and thereby be reduced and even cancelled.

FIG. 27 illustrates still another exemplary embodiment of the firsttunable RF filter path 66 in the first RF filter structure 60 shown inFIG. 21. While the exemplary embodiment shown in FIG. 27 is of the firsttunable RF filter path 66, any of the tunable RF filter paths shown inthe first RF filter structure 60 of FIG. 21 may be arranged inaccordance with the exemplary embodiment shown in FIG. 27. The firsttunable RF filter path 66 shown in FIG. 27 includes the same embodimentof the resonator R(1,1) and the same embodiment of the resonator R(1,2)described above with respect to FIG. 22. In addition, the first tunableRF filter path 66 shown in FIG. 27 includes the cross-couplingcapacitive structure C(P1) and the cross-coupling capacitive structure(CN1) that form the V-bridge structure described above with respect toFIG. 22. However, the first tunable RF filter path 66 shown in FIG. 27further includes a resonator R(1,3) and a resonator R(1,4). Morespecifically, the resonator R(1,3) includes an inductor 226, acapacitive structure 228, and a capacitive structure 230. The resonatorR(1,4) includes an inductor 232 and a capacitive structure 234.

With regard to the resonator R(1,3), the inductor 226 is electricallyconnected between the capacitive structure 228 and the capacitivestructure 230. More specifically, the inductor 226 has an end 236 and anend 238, which are disposed opposite to one another. The end 236 iselectrically connected to the capacitive structure 228 and the end 238is electrically connected to the capacitive structure 230. Both thecapacitive structure 228 and the capacitive structure 230 are grounded.Thus, the resonator R(1,3) is a differential resonator. In thisembodiment, each of the capacitive structure 228 and the capacitivestructure 230 is a variable capacitive structure.

With regard to the resonator R(1,4), the inductor 232 and the capacitivestructure 234 are electrically connected in parallel. More specifically,the inductor 232 has an end 240 and an end 242, which are disposedopposite to one another. The ends 240, 242 are each electricallyconnected to the capacitive structure 234, which is grounded. Thus, theresonator R(1,4) is a single-ended resonator.

In this embodiment, the resonator R(1,1), the resonator R(1,2), theresonator R(1,3), and the resonator R(1,4) are all weakly coupled to oneanother. The resonator R(1,3) and the resonator R(1,4) are weaklycoupled by providing the inductor 226 and the inductor 232 such that theinductor 226 and the inductor 232 are weakly coupled. The resonatorsR(1,1), R(1,2), R(1,3), and R(1,4) are each operably associated with oneanother such that energy transfer factors between the resonators R(1,1),R(1,2), R(1,3), and R(1,4) are less than 10%. Although the resonatorR(1,3) and the resonator R(1,4) are weakly coupled, the inductor 232 hasa maximum lateral width and a displacement between the inductor 226 andthe inductor 232 is less than or equal to half the maximum lateral widthof the inductor 232. As such, the inductor 226 and the inductor 232 arerelatively close to one another. The displacement between the inductor226 and the inductor 232 may be measured from a geometric centroid ofthe inductor 226 to a geometric centroid of the inductor 232. Themaximum lateral width may be a maximum dimension of the inductor 232along a plane defined by its largest winding. The weak coupling betweenthe inductor 226 and the inductor 232 is obtained through topologicaltechniques. For example, the inductor 226 and the inductor 232 may befully or partially aligned, where winding(s) of the inductor 226 andwinding(s) of the inductor 232 are configured to provide weak couplingthrough cancellation. Alternatively or additionally, a plane defining anorientation of the windings of the inductor 226 and a plane defining anorientation of the windings of the inductor 232 may be fully orpartially orthogonal to one another.

In some embodiments, all of the inductors 208, 212, 226, 232 areprovided such that displacements between each of the inductors 208, 212,226, 232 are less than or equal to half the maximum lateral width of theinductor 212. Alternatively, in other embodiments, only a proper subsetof the inductors 208, 212, 226, 232 has displacements that are less thanor equal to half the maximum lateral width of the inductor 212. Forexample, while the displacement between the inductor 208 and theinductor 212 may be less than or equal to half the maximum lateral widthof the inductor 212 and the displacement between the inductor 226 andthe inductor 232 may be less than or equal to half the maximum lateralwidth of the inductor 232, the displacements from the inductor 208 andthe inductor 212 to the inductor 226 and the inductor 232 may each begreater than half the maximum lateral width of the inductor 212 and halfthe maximum lateral width of the inductor 232.

The inductors 208, 212, 226, and 232 are magnetically coupled to theeach other such that an RF signal received at the end 217 of theinductor 208 with a voltage polarity (i.e., either a positive voltagepolarity or a negative voltage polarity) results in filtered RF signalswith the same voltage polarity being transmitted out the end 220 of theinductor 212, the end 236 of the inductor 226, and the end 240 of theinductor 232. Also, the inductors 208, 212, 226, and 232 aremagnetically coupled to the each other such that an RF signal receivedat the end 240 of the inductor 232 with a voltage polarity (i.e., eithera positive voltage polarity or a negative voltage polarity) results infiltered RF signals with the same voltage polarity being transmitted outthe end 217 of the inductor 208, the end 220 of the inductor 212, andthe end 236 of the inductor 226. This is indicated in FIG. 27 by the dotconvention where a dot is placed at the end 217 of the inductor 208, adot is placed at the end 220 of the inductor 212, a dot is placed at theend 236 of the inductor 226, and a dot is placed at the end 240 of theinductor 232.

The first tunable RF filter path 66 shown in FIG. 27 includes across-coupling capacitive structure C(P3), a cross-coupling capacitivestructure C(N3), a cross-coupling capacitive structure C(P4), and across-coupling capacitive structure C(N4) electrically connected betweenthe resonator R(1,2) and the resonator R(1,3). With respect to theresonator R(1,2) and the resonator R(1,3), the cross-coupling capacitivestructure C(P3), the cross-coupling capacitive structure C(N3), thecross-coupling capacitive structure C(P4) and the cross-couplingcapacitive structure C(N4) are arranged to have the X-bridge structuredescribed above with respect to FIG. 23. Thus, the cross-couplingcapacitive structure C(P3) is electrically connected between the end 220and the end 236 so as to provide a variable positive electric couplingcoefficient between the resonator R(1,2) and the resonator R(1,3). Thecross-coupling capacitive structure C(P3) is a variable cross-couplingcapacitive structure configured to vary the variable positive electriccoupling coefficient provided between the resonator R(1,2) and theresonator R(1,3). Also, the cross-coupling capacitive structure C(N3) iselectrically connected between the end 220 and the end 238 so as toprovide a variable negative electric coupling coefficient between theresonator R(1,2) and the resonator R(1,3). The cross-coupling capacitivestructure C(N3) is a variable cross-coupling capacitive structureconfigured to vary the variable negative electric coupling coefficientprovided between the resonator R(1,2) and the resonator R(1,3).

Additionally, the cross-coupling capacitive structure C(P4) iselectrically connected between the end 222 and the end 238 so as toprovide another variable positive electric coupling coefficient betweenthe resonator R(1,2) and the resonator R(1,3). The cross-couplingcapacitive structure C(P4) is a variable cross-coupling capacitivestructure configured to vary the other variable positive electriccoupling coefficient provided between the resonator R(1,2) and theresonator R(1,3). Finally, the cross-coupling capacitive structure C(N4)is electrically connected between the end 222 and the end 236 so as toprovide another variable negative electric coupling coefficient betweenthe resonator R(1,2) and the resonator R(1,3). The cross-couplingcapacitive structure C(N4) is a variable cross-coupling capacitivestructure configured to vary the other variable negative electriccoupling coefficient provided between the resonator R(1,2) and theresonator R(1,3).

With respect to the resonator R(1,3) and the resonator R(1,4), the firsttunable RF filter path 66 shown in FIG. 27 includes a cross-couplingcapacitive structure C(P5) and a cross-coupling capacitive structureC(N5) electrically connected between the resonator R(1,3) and theresonator R(1,4). With respect to the resonator R(1,3) and the resonatorR(1,4), the cross-coupling capacitive structure C(P5) and thecross-coupling capacitive structure C(N5) are arranged to have theV-bridge structure described above with respect to FIG. 22. Thus, thecross-coupling capacitive structure C(P5) is electrically connectedbetween the end 236 and the end 240 so as to provide a variable positiveelectric coupling coefficient between the resonator R(1,3) and theresonator R(1,4). The cross-coupling capacitive structure C(P5) is avariable cross-coupling capacitive structure configured to vary thevariable positive electric coupling coefficient provided between theresonator R(1,3) and the resonator R(1,4). Also, the cross-couplingcapacitive structure C(N5) is electrically connected between the end 238and the end 240 so as to provide a variable negative electric couplingcoefficient between the resonator R(1,3) and the resonator R(1,4). Thecross-coupling capacitive structure C(N5) is a variable cross-couplingcapacitive structure configured to vary the variable negative electriccoupling coefficient provided between the resonator R(1,3) and theresonator R(1,4).

The embodiment of first RF filter structure 60 shown in FIG. 27 alsoincludes a cross-coupling capacitive structure C(P6), a cross-couplingcapacitive structure C(N6), a cross-coupling capacitive structure C(P7),a cross-coupling capacitive structure C(N7), and a cross-couplingcapacitive structure C(P8). With respect to the resonator R(1,1) and theresonator R(1,3), the cross-coupling capacitive structure C(P6) and thecross-coupling capacitive structure C(N6) are each electricallyconnected between the resonator R(1,1) and the resonator R(1,3). Thecross-coupling capacitive structure C(P6) is electrically connectedbetween the end 217 and the end 236 so as to provide a variable positiveelectric coupling coefficient between the resonator R(1,1) and theresonator R(1,3). The cross-coupling capacitive structure C(P6) is avariable cross-coupling capacitive structure configured to vary thevariable positive electric coupling coefficient provided between theresonator R(1,1) and the resonator R(1,3). Also, the cross-couplingcapacitive structure C(N6) is electrically connected between the end 217and the end 238 so as to provide a variable negative electric couplingcoefficient between the resonator R(1,1) and the resonator R(1,3). Thecross-coupling capacitive structure C(N6) is a variable cross-couplingcapacitive structure configured to vary the variable negative electriccoupling coefficient provided between the resonator R(1,1) and theresonator R(1,3).

With respect to the resonator R(1,2) and the resonator R(1,4), thecross-coupling capacitive structure C(P7) and the cross-couplingcapacitive structure C(N7) are each electrically connected between theresonator R(1,2) and the resonator R(1,4). The cross-coupling capacitivestructure C(P7) is electrically connected between the end 220 and theend 240 so as to provide a variable positive electric couplingcoefficient between the resonator R(1,2) and the resonator R(1,4). Thecross-coupling capacitive structure C(P7) is a variable cross-couplingcapacitive structure configured to vary the variable positive electriccoupling coefficient provided between the resonator R(1,2) and theresonator R(1,4). Also, the cross-coupling capacitive structure C(N7) iselectrically connected between the end 222 and the end 240 so as toprovide a variable negative electric coupling coefficient between theresonator R(1,2) and the resonator R(1,4). The cross-coupling capacitivestructure C(N7) is a variable cross-coupling capacitive structureconfigured to vary the variable negative electric coupling coefficientprovided between the resonator R(1,2) and the resonator R(1,4).

With respect to the resonator R(1,1) and the resonator R(1,4), thecross-coupling capacitive structure C(P8) is electrically connectedbetween the resonator R(1,1) and the resonator R(1,4). Thecross-coupling capacitive structure C(P8) is electrically connectedbetween the end 217 and the end 240 so as to provide a variable positiveelectric coupling coefficient between the resonator R(1,1) and theresonator R(1,4). The cross-coupling capacitive structure C(P8) is avariable cross-coupling capacitive structure configured to vary thevariable positive electric coupling coefficient provided between theresonator R(1,1) and the resonator R(1,4).

Furthermore, in this embodiment, a variable capacitive structure 244 iselectrically connected in series between the terminal 200 and theresonator R(1,1). The variable capacitive structure 244 is configured tovary a variable impedance of the first tunable RF filter path 66 asmeasured into the terminal 200 in order to match a source or a loadimpedance at the terminal 200. In addition, a variable capacitivestructure 245 is electrically connected in series between the resonatorR(1,4) and the terminal 202. The variable capacitive structure 245 isconfigured to vary a variable impedance of the first tunable RF filterpath 66 as seen into the terminal 202 in order to match a source or aload impedance at the terminal 202.

FIGS. 28A through 28D illustrate different embodiments of the first RFfilter structure 60, wherein each of the embodiments has differentcombinations of input terminals and output terminals. The first RFfilter structure 60 can have various topologies. For example, theembodiment of the first RF filter structure 60 shown in FIG. 28A has asingle input terminal IN and an integer number i of output terminalsOUT₁-OUT_(i). As will be discussed below, the first RF filter structure60 may define various tunable RF filter paths (e.g., the first tunableRF filter path 66, the second tunable RF filter path 68, the thirdtunable RF filter path 110, the fourth tunable RF filter path 112, thefifth tunable RF filter path 122, and the sixth tunable RF filter path124 shown in FIGS. 4, 8, 11, 12, and 14-20) that may be used to receivedifferent RF signals at the input terminal IN and transmit a differentfiltered RF signal from each of the output terminals OUT₁-OUT_(i). Assuch, the first RF filter structure 60 shown in FIG. 28A may bespecifically configured to provide Single Input Multiple Output (SIMO)operations.

With regard to the embodiment of the first RF filter structure 60 shownin FIG. 28B, the first RF filter structure 60 has an integer number j ofinput terminals IN₁-IN_(j) and a single output terminal OUT. As will bediscussed below, the first RF filter structure 60 may define varioustunable RF filter paths (e.g., the first tunable RF filter path 66, thesecond tunable RF filter path 68, the third tunable RF filter path 110,the fourth tunable RF filter path 112, the fifth tunable RF filter path122, and the sixth tunable RF filter path 124 shown in FIGS. 4, 8, 11,12, and 14-20) that may be used to receive a different RF signal at eachof the input terminals IN₁-IN_(j) and transmit different filtered RFsignals from the single output terminal OUT. As such, the first RFfilter structure 60 shown in FIG. 28B may be specifically configured toprovide Multiple Input Single Output (MISO) operations.

With regard to the embodiment of the first RF filter structure 60 shownin FIG. 28C, the first RF filter structure 60 has a single inputterminal IN and a single output terminal OUT. As will be discussedbelow, the first RF filter structure 60 may define various tunable RFfilter paths (e.g., the first tunable RF filter path 66, the secondtunable RF filter path 68, the third tunable RF filter path 110, thefourth tunable RF filter path 112, the fifth tunable RF filter path 122,and the sixth tunable RF filter path 124 shown in FIGS. 4, 8, 11, 12,and 14-20) that may be used to receive different RF signals at thesingle input terminal IN and transmit different filtered RF signals fromthe output terminal OUT. As such, the first RF filter structure 60 shownin FIG. 28A may be specifically configured to provide Single InputSingle Output (SISO) operations.

With regard to the embodiment of the first RF filter structure 60 shownin FIG. 28D, the first RF filter structure 60 has the input terminalsIN₁-IN_(j) and the output terminals OUT₁-OUT_(i). As will be discussedbelow, the first RF filter structure 60 may define various tunable RFfilter paths (e.g., the first tunable RF filter path 66, the secondtunable RF filter path 68, the third tunable RF filter path 110, thefourth tunable RF filter path 112, the fifth tunable RF filter path 122,and the sixth tunable RF filter path 124 shown in FIGS. 4, 8, 11, 12,and 14-20) that may be used to receive a different RF signal at each ofthe input terminal IN₁-IN_(j) and transmit a different filtered RFsignal from each of the output terminals OUT₁-OUT_(i).

FIG. 29 illustrates another embodiment of the first RF filter structure60. The first RF filter structure 60 shown in FIG. 29 includes oneembodiment of the first tunable RF filter path 66 and one embodiment ofthe second tunable RF filter path 68. The first tunable RF filter path66 includes the resonator R(1,1) and the resonator R(1,2). The resonatorR(1,1) and the resonator R(1,2) are thus a first pair of weakly coupledresonators in the first tunable RF filter path 66. The second tunable RFfilter path 68 includes the resonator R(2,1) and the resonator R(2,2).The resonator R(2,1) and the resonator R(2,2) are thus a second pair ofweakly coupled resonators in the second tunable RF filter path 68.

As explained in further detail below, a set S of cross-couplingcapacitive structures is electrically connected between the resonatorR(1,1), the resonator R(1,2), the resonator R(2,1), and the resonatorR(2,2) in the first tunable RF filter path 66 and the second tunable RFfilter path 68. More specifically, the set S includes a cross-couplingcapacitive structure C(PM1), a cross-coupling capacitive structureC(PM2), a cross-coupling capacitive structure C(PM3), a cross-couplingcapacitive structure C(PM4), a cross-coupling capacitive structureC(NM1), and a cross-coupling capacitive structure C(NM2). The set S ofcross-coupling capacitive structures interconnects the resonator R(1,1),the resonator R(1,2), the resonator R(2,1), and the resonator R(2,2) sothat the first RF filter structure 60 shown in FIG. 29 is a matrix (inthis embodiment, a 2×2 matrix) of the resonators R. In alternativeembodiments, some of the cross-coupling capacitive structures C(PM1),C(PM2), C(PM3), C(PM4), C(NM1), and C(NM2) may be omitted depending onthe filter transfer function to be provided.

Unlike in the embodiment of the first RF filter structure 60 shown inFIG. 21, in this embodiment, the first tunable RF filter path 66 and thesecond tunable RF filter path 68 are not independent of one another. Theset S of cross-coupling capacitive structures thus provides foradditional tunable RF filter paths to be formed from the resonatorR(1,1), the resonator R(1,2), the resonator R(2,1), and the resonatorR(2,2). As discussed in further detail below, the arrangement of thefirst RF filter structure 60 shown in FIG. 29 can be used to realizeexamples of each of the embodiments of the first RF filter structure 60shown in FIGS. 28A-28D.

The cross-coupling capacitive structure C(PM1) is electrically connectedwithin the first tunable RF filter path 66, while the cross-couplingcapacitive structure C(PM4) is electrically connected within the secondtunable RF filter path 68. More specifically, the cross-couplingcapacitive structure C(PM1) is electrically connected between theresonator R(1,1) and the resonator R(1,2) in the first tunable RF filterpath 66. The cross-coupling capacitive structure C(PM1) is a variablecross-coupling capacitive structure configured to provide and vary a(e.g., positive or negative) electric coupling coefficient between theresonator R(1,1) and the resonator R(1,2). The cross-coupling capacitivestructure C(PM4) is a variable cross-coupling capacitive structureconfigured to provide and vary a (e.g., positive or negative) electriccoupling coefficient between the resonator R(2,1) and the resonatorR(2,2) in the second tunable RF filter path 68.

To provide additional tunable RF filter paths, the cross-couplingcapacitive structure C(PM2), the cross-coupling capacitive structureC(PM3), the cross-coupling capacitive structure C(NM1), and thecross-coupling capacitive structure C(NM2) are each electricallyconnected between the first tunable RF filter path 66 and the secondtunable RF filter path 68. The cross-coupling capacitive structureC(PM2) is a variable cross-coupling capacitive structure configured toprovide and vary a (e.g., positive or negative) electric couplingcoefficient between the resonator R(1,2) and the resonator R(2,2). Thecross-coupling capacitive structure C(PM3) is a variable cross-couplingcapacitive structure configured to provide and vary a (e.g., positive ornegative) electric coupling coefficient between the resonator R(1,1) andthe resonator R(2,1). The cross-coupling capacitive structure C(NM1) isa variable cross-coupling capacitive structure configured to provide andvary a (e.g., positive or negative) electric coupling coefficientbetween the resonator R(1,1) and the resonator R(2,2). Thecross-coupling capacitive structure C(NM2) is a variable cross-couplingcapacitive structure configured to provide and vary a (e.g., positive ornegative) electric coupling coefficient between the resonator R(1,2) andthe resonator R(2,1).

The first tunable RF filter path 66 is electrically connected betweenthe input terminal IN₁ and the output terminal OUT₁. In addition, thesecond tunable RF filter path 68 is electrically connected between aninput terminal IN₂ and an output terminal OUT₂. Accordingly, the firstRF filter structure 60 shown in FIG. 29 is an embodiment of the first RFfilter structure 60 shown in FIG. 28D. However, the input terminal IN₂and the output terminal OUT₁ are optional and may be excluded in otherembodiments. For example, if the input terminal IN₂ were not provided,but the output terminal OUT₁ and the output terminal OUT₂ were provided,the first RF filter structure 60 shown in FIG. 29 would be provided asan embodiment of the first RF filter structure 60 shown in FIG. 28A. Itmight, for example, provide a diplexing or a duplexing function.Furthermore, more than two input terminals or output terminals can beprovided. Some examples include embodiments of the first RF filterstructure 60 used for triplexing, quadplexing, herplexing, and providingFDD and carrier aggregation.

The first tunable RF filter path 66 still provides a path between theinput terminal IN₁ and the output terminal OUT₁. However, assuming thatthe input terminal IN₂ is not provided for SIMO operation, thecross-coupling capacitive structure C(NM1) is electrically connectedbetween the first tunable RF filter path 66 and the second tunable RFfilter path 68 to define a first additional tunable RF filter pathbetween the input terminal IN₁ and the output terminal OUT₂. The firstadditional tunable RF filter path is thus provided by a portion of thefirst tunable RF filter path 66 and a portion of the second tunable RFfilter path 68. More specifically, the first additional tunable RFfilter path includes the resonator R(1,1) and the resonator R(2,2). Thefirst additional tunable RF filter path also includes the cross-couplingcapacitive structure C(NM1) that is electrically connected between theresonator R(1,1) and the resonator R(1,2). A second additional tunableRF filter path, a third additional tunable RF filter path, a fourthadditional tunable RF filter path, and a fifth additional tunable RFfilter path are also defined from the input terminal IN₁ to the outputterminal OUT₂. The second additional tunable RF filter path includes theresonator R(1,1), the cross-coupling capacitive structure C(PM1), theresonator R(1,2), the cross-coupling capacitive C(PM2), and theresonator R(2,2). Additionally, the third additional tunable RF filterpath includes the resonator R(1,1), the cross-coupling capacitivestructure C(PM3), the resonator R(2,1), the cross-coupling capacitiveC(PM4), and the resonator R(2,2). The fourth additional tunable RFfilter path includes the resonator R(1,1), the cross-coupling capacitivestructure C(PM1), the resonator R(1,2), the cross-coupling capacitiveC(NM2), the resonator R(2,1), the cross-coupling capacitive structureC(PM4), and the resonator R(2,2). Finally, the fifth additional tunableRF filter path includes the resonator R(1,1), the cross-couplingcapacitive structure C(PM3), the resonator R(2,1), the cross-couplingcapacitive C(NM2), the resonator R(1,2), the cross-coupling capacitivestructure C(PM2), and the resonator R(2,2).

If the output terminal OUT₁ were not provided, but the input terminalIN₁ and the input terminal IN₂ were provided, the first RF filterstructure 60 shown in FIG. 29 would be provided as an embodiment of thefirst RF filter structure 60 shown in FIG. 28B. In this case, the secondtunable RF filter path 68 still provides a path between the inputterminal IN₂ and the output terminal OUT₂. However, assuming that theoutput terminal OUT₁ is not provided for MISO operation, the firstadditional tunable RF filter path, the second additional tunable RFfilter path, the third additional tunable RF filter path, the fourthadditional tunable RF filter path, and the fifth additional tunable RFfilter path would provide the paths from the input terminal IN₁ to theoutput terminal OUT₂.

Finally, if the input terminal IN₂ and the output terminal OUT₂ were notprovided, the first RF filter structure 60 shown in FIG. 29 would beprovided as an embodiment of the first RF filter structure 60 shown inFIG. 28C. In this case, the second tunable RF filter path 68 stillprovides a path between the input terminal IN₂ and the output terminalOUT₂. However, assuming that the output terminal IN₁ is not provided forMISO operation, the first additional tunable RF filter path, the secondadditional tunable RF filter path, the third additional tunable RFfilter path, the fourth additional tunable RF filter path, and the fifthadditional tunable RF filter path would provide the paths from the inputterminal IN₁ to the output terminal OUT₂. This may constitute a SISOfilter implemented with an array to allow for a large number of signalpaths and thus create one or more notches in the transfer function.

With regard to the resonators R(1,1), R(1,2), R(2,1), R(2,2) shown inFIG. 29, the resonators R(1,1), R(1,2), R(2,1), R(2,2) may each besingle-ended resonators, differential resonators, or differentcombinations of single-ended resonators and differential resonators. Theresonator R(1,1) and the resonator R(1,2) in the first tunable RF filterpath 66 may each be provided in accordance with any of the embodimentsof the resonator R(1,1) and the resonator R(1,2) described above withrespect to FIGS. 22-27. For example, the resonator R(1,1) may includethe inductor 208 (see FIG. 24) and the capacitive structure 210 (seeFIG. 24). The resonator R(1,2) may include the inductor 212 and thecapacitive structure 214 (see FIG. 24). The resonator R(2,1) may includean inductor (like the inductor 208 in FIG. 24) and a capacitivestructure (like the capacitive structure 210 shown in FIG. 24). Theresonator R(2,2) may include an inductor (like the inductor 212 in FIG.24) and a capacitive structure (like the capacitive structure 214 shownin FIG. 24).

Additionally, one or more of the resonators R(1,1), R(1,2) in the firsttunable RF filter path 66 and one or more of the resonators R(2,1),R(2,2) in the second tunable RF filter path 68 may be weakly coupled.Thus, the resonators R(1,1), R(1,2), R(2,1), R(2,2) may be operablyassociated with one another such that an energy transfer factor betweeneach of the resonators R(1,1), R(1,2), R(2,1), R(2,2) is less than 10%.Alternatively, the energy transfer factor between only a subset of theresonators R(1,1), R(1,2), R(2,1), R(2,2) is less than 10%. In addition,in at least some embodiments, not all of the resonators R(1,1), R(1,2),R(2,1), R(2,2) are weakly coupled to one another.

In this embodiment, the inductor 208 (see FIG. 24) of the resonatorR(1,1), the inductor 212 (see FIG. 24) of the resonator R(1,2), theinductor of the resonator R(2,1), and the inductor of the resonatorR(2,2) may all be weakly coupled to one another. In some embodiments,displacements between the inductor 208 (see FIG. 24) of the resonatorR(1,1), the inductor 212 (see FIG. 24) of the resonator R(1,2), theinductor of the resonator R(2,1), and the inductor of the resonatorR(2,2) may all be less than or equal to half the maximum lateral widthof the inductor 212. Alternatively, in other embodiments, only a propersubset of the inductor 208 (see FIG. 24) of the resonator R(1,1), theinductor 212 (see FIG. 24) of the resonator R(1,2), the inductor of theresonator R(2,1), and the inductor of the resonator R(2,2) may havedisplacements that are less than or equal to half the maximum lateralwidth of the inductor 212.

FIG. 30 illustrates yet another embodiment of the first RF filterstructure 60. The first RF filter structure 60 includes the resonators Rdescribed above with respect to FIG. 21. The resonators R of the firstRF filter structure 60 shown in FIG. 30 are arranged as atwo-dimensional matrix of the resonators R. In this embodiment, thefirst RF filter structure 60 includes an embodiment of the first tunableRF filter path 66, an embodiment of the second tunable RF filter path68, an embodiment of the third tunable RF filter path 110, and anembodiment of the fourth tunable RF filter path 112. Thus, the integer Mfor the first RF filter structure 60 shown in FIG. 30 is four (4) orgreater. Additionally, the integer N for the first RF filter structure60 shown in FIG. 30 is 3 or greater. Note that in alternativeembodiments, the integer M may be two (2) or greater and the integer Nmay be two (2) or greater. It should be noted that in alternativeembodiments the number of resonators R in each row and column may be thesame or different.

In the embodiment of the first RF filter structure 60 shown in FIG. 30,the first tunable RF filter path 66 includes the resonator R(1,1), theresonator R(1,2), and one or more additional resonators R, such as theresonator R(1,N), since the integer N is 3 or greater. All of the weaklycoupled resonators R(1,1) through R(1,N) are weakly coupled to oneanother. Furthermore, the first tunable RF filter path 66 iselectrically connected between a terminal TU1 and a terminal TANT1. Withregard to the second tunable RF filter path 68, the second tunable RFfilter path 68 includes the resonator R(2,1), the resonator R(2,2), andone or more additional resonators R, such as the resonator R(2,N), sincethe integer N is 3 or greater. All of the weakly coupled resonatorsR(2,1) through R(2,N) are weakly coupled to one another. Furthermore,the second tunable RF filter path 68 is electrically connected between aterminal TU2 and a terminal TANT2.

With regard to the third tunable RF filter path 110, the third tunableRF filter path 110 includes a resonator R(3,1), a resonator R(3,2), andone or more additional resonators R, such as a resonator R(3,N), sincethe integer N is 3 or greater. All of the weakly coupled resonatorsR(3,1) through R(3,N) are weakly coupled to one another. Alternatively,only a proper subset of them may be weakly coupled to one another.Furthermore, the third tunable RF filter path 110 is electricallyconnected between a terminal TU3 and a terminal TANT3. With regard tothe fourth tunable RF filter path 112, the fourth tunable RF filter path112 includes the resonator R(M,1), the resonator R(M,2), and one or moreadditional resonators R, such as the resonator R(M,N), since the integerN is 3 or greater. All of the weakly coupled resonators R(M,1) throughR(M,N) are weakly coupled to one another. Alternatively, only a propersubset of them may be weakly coupled to one another. Furthermore, thefourth tunable RF filter path 112 is electrically connected between aterminal TU4 and a terminal TANT4.

The first tunable RF filter path 66 is configured to receive RF signalsand output filtered RF signals. It should be noted that the first RFfilter structure 60 may include any number of tunable RF filter paths,such as, for example, the third tunable RF filter path 110, the fourthtunable RF filter path 112, the fifth tunable RF filter path 122, andthe sixth tunable RF filter path 124, described above with respect toFIGS. 11-14. Each of the resonators R may be a tunable resonator, whichallows for a resonant frequency of each of the resonators to be variedto along a frequency range. In alternative embodiments, only a propersubset of the resonators R may be tunable. In still another embodiment,all of the resonators R are not tunable, but rather have a fixedtransfer function.

In some embodiments, all of the resonators R in the first RF filterstructure 60 shown in FIG. 30 are weakly coupled to one another. Thus,the resonators R may all be operably associated with one another suchthat energy transfer factors between the resonators R are less than 10%.Alternatively, the energy transfer factor is less than 10% only among aproper subset of the resonators R. In other embodiments, only theresonators R in adjacent tunable RF filter paths 66, 68, 110, 112 areweakly coupled to one another. For example, all the resonators R(1,1)through R(1,N) may be weakly coupled to all the resonators R(2,1)through R(2,N). In still other embodiments, only subsets of adjacentresonators R may be weakly coupled to each other. For example, theresonators R(1,1), R(1,2) may be weakly coupled to the resonatorsR(2,1), R(2,2), while the resonators R(3,1), R(3,2) may be weaklycoupled to the resonators R(M,1), R(M,2). These and other combinationswould be apparent to one of ordinary skill in the art in light of thisdisclosure.

Sets S(1), S(2), S(3), S(4), S(5), and S(6) of cross-coupled capacitivestructures are electrically connected between the resonators R. Each ofthe sets S(1), S(2), S(3), S(4), S(5), and S(6) is arranged like the setS of cross-coupled capacitive structures described above with respect toFIG. 29. For example, in one particular exemplary embodiment (e.g., whenM=4 and N=3), the set S(1) of cross-coupled capacitive structures iselectrically connected between the resonators R(1,1), R(1,2) in thefirst tunable RF filter path 66 and the resonators R(2,1), R(2,2) in thesecond tunable RF filter path 68. The set S(2) of cross-coupledcapacitive structures is electrically connected between the resonatorsR(1,2), R(1,N) in the first tunable RF filter path 66 and the resonatorsR(2,2), R(2,N) in the second tunable RF filter path 68. The set S(3) ofcross-coupled capacitive structures is electrically connected betweenthe resonators R(2,1), R(2,2) in the second tunable RF filter path 68and the resonators R(3,1), R(3,2) in the third tunable RF filter path110. The set S(4) of cross-coupled capacitive structures is electricallyconnected between the resonators R(2,2), R(2,N) in the second tunable RFfilter path 68 and the resonators R(3,2), R(3,N) in the third tunable RFfilter path 110. The set S(5) of cross-coupled capacitive structures iselectrically connected between the resonators R(3,1), R(3,2) in thethird tunable RF filter path 110 and the resonators R(M,1), R(M,2) inthe fourth tunable RF filter path 112. Finally, the set S(6) ofcross-coupled capacitive structures is electrically connected betweenthe resonators R(3,2), R(3,N) in the third tunable RF filter path 110and the resonators R(M,2), R(M,N) in the fourth tunable RF filter path112. Note that some cross-coupled capacitive structures in the setsS(1), S(2), S(3), S(4), S(5), and S(6) of cross-coupled capacitivestructures for the resonators R in adjacent columns or in adjacent onesof the tunable RF filter paths 66, 68, 110, 112 overlap. This is becausein the matrix of the resonators R, each of the resonators R is adjacentto multiple other ones of the resonators R. In another embodiment, thesets S(1), S(2), S(3), S(4), S(5), and S(6) of cross-coupled capacitivestructures may be connected between non-adjacent resonators R. Forexample, there may be cross-coupled capacitive structures betweenresonators R that are more than one column or row apart.

FIG. 31 illustrates the embodiment of the first RF filter structure 60shown in FIG. 30 electrically connected to the first RF antenna 16, thesecond RF antenna 32, a third RF antenna 246, and a fourth RF antenna247. More specifically, the first tunable RF filter path 66 iselectrically connected to the first RF antenna 16 at the terminal TANT1.The second tunable RF filter path 68 is electrically connected to thesecond RF antenna 32 at the terminal TANT2. The third tunable RF filterpath 110 is electrically connected to the third RF antenna 246 at theterminal TANT3. The fourth tunable RF filter path 112 is electricallyconnected to the fourth RF antenna 247 at the terminal TANT4. With thesets S(1), S(2), S(3), S(4), S(5), and S(6) of cross-coupled capacitivestructures, the first RF filter structure 60 shown in FIG. 31 forms aninterconnected two-dimensional matrix of the resonators R. Thus, inaddition to the first tunable RF filter path 66, the second tunable RFfilter path 68, the third tunable RF filter path 110, and the fourthtunable RF filter path 112, the sets S(1), S(2), S(3), S(4), S(5), andS(6) of cross-coupled capacitive structures provide a multitude ofadditional tunable RF filter paths between the terminals TU1, TU2, TU3,TU4 and the terminals TANT1, TANT2, TANT3, TANT4. It should be notedthat in alternative embodiments, the terminals TANT1, TANT2, TANT3,TANT4 may not be connected to antennas. Some antennas may be omitteddepending on the functionality being realized.

By tuning the sets S(1), S(2), S(3), S(4), S(5), and S(6), the first RFfilter structure 60 shown in FIG. 31 can be tuned so that anycombination of the resonators R is selectable for the propagation of RFsignals. More specifically, the first RF filter structure 60 shown inFIG. 31 is tunable to route RF receive signals from any combination ofthe terminals TANT1, TANT2, TANT3, TANT4 to any combination of theterminals TU1, TU2, TU3, TU4. Additionally, the first RF filterstructure 60 shown in FIG. 31 is tunable to route RF transmissionsignals from any combination of the terminals TU1, TU2, TU3, TU4 to theterminals TANT1, TANT2, TANT3, TANT4. Accordingly, the first RF filterstructure 60 can be configured to implement various MIMO, SIMO, MISO,and SISO operations.

FIG. 32 illustrates the first RF filter structure 60 shown in FIGS. 30and 31 with examples of additional tunable RF filter paths 248, 250highlighted. It should be noted, however, that there are a vast numberof additional combinations of the resonators R that may be selected toprovide tunable RF filter paths (e.g., the first tunable RF filter path66, the second tunable RF filter path 68, the third tunable RF filterpath 110, the fourth tunable RF filter path 112, the additional tunableRF filter path 248, and the additional tunable RF filter path 250)between the terminals TU1, TU2, TU3, TU4 and the terminals TANT1, TANT2,TANT3, TANT4. An explicit description of all of the various combinationsof the resonators R that may be implemented with the first RF filterstructure 60 shown in FIGS. 30-32 is simply impractical given the highnumber of possible combinations. Along with the previous descriptions,the additional tunable RF filter paths 248, 250 are highlighted in FIG.32 simply to give examples of the basic concepts. However, thecombinations provided for the additional tunable RF filter paths 248,250 are in no way limiting, as any combination of the resonators R maybe selected to route RF signals between the terminals TU1, TU2, TU3, TU4and the terminals TANT1, TANT2, TANT3, TANT4. Any number of functions,such as signal combining, splitting, multiplexing, and demultiplexing,with various filtering profiles for each, may be realized.

With regard to the additional tunable RF filter paths 248, 250highlighted in FIG. 32, the additional tunable RF filter paths 248, 250may be used during MIMO, SIMO, MISO, and SISO operations. Morespecifically, the additional tunable RF filter path 248 connects theterminal TANT1 to the terminal TU2. The additional tunable RF filterpath 250 connects the terminal TANT3 to the terminal TU2. As such, thefirst RF filter structure 60 may be tuned so that the additional tunableRF filter path 248 and the additional tunable RF filter path 250 areselected in a MISO operation from the terminal TANT1 and the terminalTANT3 to the terminal TU2. The additional tunable RF filter paths 248,250 may also be used in SIMO operations. For example, the first RFfilter structure 60 may be tuned so that the first tunable RF filterpath 66 and the additional tunable RF filter path 248 are selected in aSIMO operation from the terminal TU2 to the terminal TANT1. Theadditional tunable RF filter paths 248, 250 can also be used in SISOoperations from the terminal TANT1 to the terminal TU2 or from theterminal TANT3 to the terminal TU2. Finally, the additional tunable RFfilter paths 248, 250 may also be used in SIMO operations. For instance,the first RF filter structure 60 may be tuned so that the first tunableRF filter path 66 and the additional tunable RF filter path 250 areselected in a SIMO operation from the terminal TANT1 to the terminal TU1and from the terminal TANT3 to the terminal TU2.

In some applications involving the first RF filter structure 60 in FIGS.30-32, MISO and SIMO operations can be used in conjunction with widebandantenna cables or fiber for transmitting RF signals in multiple RFcommunication frequency bands. Specific communication frequency bandscan be processed by certain dedicated RF filtering paths in the first RFfilter structure 60. For example, different RF signals may be injectedfrom a wideband antenna and then propagated along different dedicatedtunable RF filter paths in the first RF filter structure 60 to theterminals TU1, TU2, TU3, TU4. These dedicated tunable RF filter pathscan be configured to have a transfer function that is specificallydesigned to handle these RF signals. Furthermore, the first RF filterstructure 60 shown in FIGS. 30-32 is configured to tune a transferfunction of any of the specific tunable RF filter paths (e.g., the firsttunable RF filter path 66, the second tunable RF filter path 68, thethird tunable RF filter path 110, the fourth tunable RF filter path 112,the additional tunable RF filter path 248, and the additional tunable RFfilter path 250) in the first RF filter structure 60 by tuningresonators R that are not in the specific tunable RF filter path beingused to route RF signals. This can help reduce out-of-band noise andreduce insertion losses. It can also improve isolation and out-of-bandattenuation.

FIG. 33 illustrates yet another embodiment of the first RF filterstructure 60. The first RF filter structure 60 includes the resonators Rand is arranged as a two-dimensional matrix of the resonators R, where Nis equal to four (4) and M is equal to three (3). In this embodiment,the first RF filter structure 60 includes an embodiment of the firsttunable RF filter path 66, an embodiment of the second tunable RF filterpath 68, and an embodiment of the third tunable RF filter path 110. Itshould be noted that in alternative embodiments, the number ofresonators R in each row and column may be the same or different.

In the embodiment of the first RF filter structure 60 shown in FIG. 33,the first tunable RF filter path 66 includes the resonator R(1,1), theresonator R(1,2), the resonator R(1,3), and the resonator R(1,4).Furthermore, the first tunable RF filter path 66 is electricallyconnected between the terminal TU1 and the terminal TANT1. With regardto the second tunable RF filter path 68, the second tunable RF filterpath 68 includes the resonator R(2,1), the resonator R(2,2), a resonatorR(2,3), and a resonator R(2,4). Furthermore, the second tunable RFfilter path 68 is electrically connected between the terminal TU2 andthe terminal TANT2. With regard to the third tunable RF filter path 110,the third tunable RF filter path 110 includes the resonator R(3,1), theresonator R(3,2), a resonator R(3,3), and a resonator R(3,4).Furthermore, the third tunable RF filter path 110 is electricallyconnected between the terminal TU3 and the terminal TANT3.

In this embodiment, the resonators R in a subset 252 of the resonatorsR(1,1), R(1,2) in the first tunable RF filter path 66 are weakly coupledto one another. A cross-coupling capacitive structure CS1 iselectrically connected between the resonators R(1,1), R(1,2). Thecross-coupling capacitive structure CS1 is a variable cross-couplingcapacitive structure configured to vary a variable electric couplingcoefficient between the resonators R(1,1), R(1,2). A subset 254 of theresonators R(1,3), and R(1,4) in the second tunable RF filter path 68 isalso weakly coupled to each other. A cross-coupling capacitive structureCS2 is electrically connected between the resonators R(1,3), R(1,4). Thecross-coupling capacitive structure CS2 is a variable cross-couplingcapacitive structure configured to vary a variable electric couplingcoefficient between the resonators R(1,3), R(1,4).

As shown in FIG. 33, a unidirectional coupling stage 256 is electricallyconnected within the first tunable RF filter path 66. The unidirectionalcoupling stage 256 defines an amplifier gain and is configured toprovide amplification within the first tunable RF filter path 66 inaccordance with the amplifier gain. In some embodiments, the amplifiergain of the unidirectional coupling stage 256 is a variable amplifiergain. In this embodiment, the unidirectional coupling stage 256 iselectrically connected between the resonator R(1,2) and the resonatorR(1,3). The variable amplifier gain can thus control a variable electriccoupling coefficient between the resonator R(1,2) in the subset 252 andthe resonator R(1,3) in the subset 254. Since the unidirectionalcoupling stage 256 is an active semiconductor component, theunidirectional coupling stage 256 is unidirectional and thus only allowssignal propagations from an input terminal IA of the unidirectionalcoupling stage 256 to an output terminal OA of the unidirectionalcoupling stage 256. Thus, the resonator R(1,2) in the subset 252 isunidirectionally mutual electrically coupled to the resonator R(1,3) inthe subset 254.

Note that the resonators R(1,3), R(1,4) in the subset 254 are notelectrically connected to the second tunable RF filter path 68 and thethird tunable RF filter path 110. As such, the unidirectional couplingstage 256 thus results in a portion of the first tunable RF filter path66 with the subset 254 of the resonators R(1,3), R(1,4) to beunidirectional. Consequently, signal flow can be to the terminal TANT1but not from the terminal TANT1. Since the unidirectional coupling stage256 is unidirectional, the variable amplifier gain (and thus thevariable electric coupling coefficient between the resonator R(1,2) andthe resonator R(1,3)) may be controlled using feed-forward controltechniques and/or feedback control techniques.

Next, the resonators R in a subset 258 of the resonators R(2,1), R(2,2),R(3,1), and R(3,2) in the second tunable RF filter path 68 and in thethird tunable RF filter path 110 are weakly coupled to one another. Anunidirectional coupling stage 260 is electrically connected between thefirst tunable RF filter path 66 and the second tunable RF filter path68. More specifically, the unidirectional coupling stage 260 iselectrically connected between the resonator R(1,1) and the resonatorR(2,1). The unidirectional coupling stage 260 defines an amplifier gainand is configured to provide amplification in accordance with theamplifier gain. In some embodiments, the amplifier gain of theunidirectional coupling stage 260 is a variable amplifier gain. Thevariable amplifier gain thus can control a variable electric couplingcoefficient between the resonator R(1,1) in the subset 252 and theresonator R(2,1) in the subset 258. A cross-coupling capacitivestructure CS3 is electrically connected between the resonator R(1,2) andthe resonator R(2,2). The cross-coupling capacitive structure CS3 is avariable cross-coupling capacitive structure configured to vary avariable electric coupling coefficient between the resonators R(1,2),R(2,2).

To interconnect the resonators R(2,1), R(2,2), R(3,1), and R(3,2), a setS(A) of cross-coupling capacitive structures is electrically connectedbetween the resonators R(2,1), R(2,2), R(3,1), and R(3,2) in the subset258. The set S(A) of cross-coupling capacitive structures is arrangedlike the set S of cross-coupling capacitive structures described abovewith respect to FIG. 29. Additionally, the resonators R in a subset 262of the resonators R(2,3), R(2,4), R(3,3), and R(3,4) in the secondtunable RF filter path 68 and in the third tunable RF filter path 110are weakly coupled to one another. A set S(B) of cross-couplingcapacitive structures is electrically connected between the resonatorsR(2,3), R(2,4), R(3,3), and R(3,4) in the subset 262. The set S(B) ofcross-coupling capacitive structures is arranged like the set S ofcross-coupling capacitive structures described above with respect toFIG. 29.

To interconnect the subset 258 and the subset 262, the first RF filterstructure 60 shown in FIG. 33 includes a cross-coupling capacitivestructure CS4 and a unidirectional coupling stage 264. Thecross-coupling capacitive structure CS4 is electrically connectedbetween the resonators R(2,2), R(2,3). The cross-coupling capacitivestructure CS4 is a variable cross-coupling capacitive structureconfigured to vary a variable electric coupling coefficient between theresonators R(2,2), R(2,3). The unidirectional coupling stage 264 iselectrically connected within the third tunable RF filter path 110. Inthis embodiment, the unidirectional coupling stage 264 is electricallyconnected between the resonator R(3,3) and the resonator R(3,2). Theunidirectional coupling stage 264 defines an amplifier gain and isconfigured to provide amplification within the third tunable RF filterpath 110 in accordance with the amplifier gain. In some embodiments, theamplifier gain of the unidirectional coupling stage 264 is a variableamplifier gain. The variable amplifier gain can thus control a variableelectric coupling coefficient between the resonator R(3,3) in the subset262 and the resonator R(3,2) in the subset 258. Since the unidirectionalcoupling stage 264 is an active semiconductor component, theunidirectional coupling stage 264 is unidirectional and thus only allowssignal propagations from an input terminal IB of the unidirectionalcoupling stage 264 to an output terminal OB of the unidirectionalcoupling stage 264. Thus, the resonator R(3,3) in the subset 262 isunidirectionally mutual electrically coupled to the resonator R(3,2) inthe subset 258. Consequently, the third tunable RF filter path 110 shownin FIG. 33 is unidirectional if the signal flow is between the terminalTANT3 and the terminal TU3 though the third tunable RF filter path 110.As such signal flow between the terminal TANT3 and the terminal TU3 isprovided only through the third tunable RF filter path 110, signal flowcan only be from the terminal TANT3 to the terminal TU3, and not viceversa. In other cases, an additional tunable RF signal path (e.g., theadditional RF terminal tunable RF signal path that includes theresonators R(3,1), R(2,2), R(2,3) and R(3,4)) can be tuned to providebidirectional signal flow between the terminal TU3 and the terminalTANT3 through the cross-coupling capacitive structure CS4. Theunidirectional coupling stages 256, 260, 264 may be active devices, suchas amplifiers, diodes, transistors, networks of transistors, bufferstages, attenuation stages, and the like. The unidirectional couplingstages 256, 260, 264 can have gains higher than one (1), lower than one(1), or equal to one (1). Additionally, the unidirectional couplingstages 256, 260, 264 may be passive devices. The unidirectional couplingstages 256, 260, 264 may not be entirely or ideally unilateral, but mayhave some finite reverse coupling. In this case, the unidirectionalcoupling stages 256, 260, 264 may be predominately unilateral. Oneexample in which the unidirectional coupling stages 256, 260, 264 may beused for multi-resonator applications and may improve isolation betweencertain parts, such as transmission ports and receive ports of aduplexer.

FIG. 34 illustrates yet another embodiment of the first RF filterstructure 60. The first RF filter structure 60 shown in FIG. 34 isintegrated into an IC package 266. The first RF filter structure 60shown in FIG. 34 includes the resonators R and is arranged as atwo-dimensional matrix of the resonators R, where N is equal to three(3) and M is equal to two (2). It should be noted that in alternativeembodiments the number of resonators R in each row and column may be thesame or different.

In this embodiment, the first RF filter structure 60 includes anembodiment of the first tunable RF filter path 66 and an embodiment ofthe second tunable RF filter path 68. The first tunable RF filter path66 includes the resonator R(1,1), the resonator R(1,2), and theresonator R(1,3). The second tunable RF filter path 68 includes theresonator R(2,1), the resonator R(2,2), and the resonator R(2,3). A setS(X) of cross-coupling capacitive structures is electrically connectedbetween the resonators R(1,1), R(1,2), R(2,1), and R(2,2). The set S(X)of cross-coupling capacitive structures is arranged like the set S ofcross-coupling capacitive structures described above with respect toFIG. 29. A set S(Y) of cross-coupling capacitive structures iselectrically connected between the resonators R(1,2), R(1,3), R(2,2),and R(2,3). The set S(Y) of cross-coupling capacitive structures is alsoarranged like the set S of cross-coupling capacitive structuresdescribed above with respect to FIG. 29.

As shown in FIG. 34, the IC package 266 houses a package substrate 268,a semiconductor die 270, and a semiconductor die 272. The semiconductordie 270 and the semiconductor die 272 are mounted on the packagesubstrate 268. In this embodiment, the resonators R of the first RFfilter structure 60 are formed by the package substrate 268. The setS(X) of cross-coupling capacitive structures is formed by thesemiconductor die 270. On the other hand, the set S(Y) of cross-couplingcapacitive structures is formed by the semiconductor die 272. Thus, theset S(X) of cross-coupling capacitive structures and the set S(Y) ofcross-coupling capacitive structures are formed on multiple and separatesemiconductor dies 270, 272. Using the multiple and separatesemiconductor dies 270, 272 may be helpful in order to increaseisolation. The multiple and separate semiconductor dies 270, 272 mayhave less area than the semiconductor die 268 shown in FIG. 34. As such,the embodiment shown in FIG. 35 may consume less die area.

FIG. 35 illustrates another embodiment of an IC package 266′ that housesthe same embodiment of the first RF filter structure 60 described abovewith regard to FIG. 34. The IC package 266′ is the same as the ICpackage 266 shown in FIG. 34, except that the IC package 266′ only has asingle semiconductor die 274. In this embodiment, both the set S(X) ofcross-coupling capacitive structures and the set S(Y) of cross-couplingcapacitive structures are formed by the semiconductor die 272. Thus, theIC package 266′ allows for a more compact arrangement than the ICpackage 266.

FIG. 36 illustrates yet another embodiment of the first RF filterstructure 60. In this embodiment, the first RF filter structure 60 isarranged as a three-dimensional matrix of resonators R1, R2, R3. Morespecifically, a two-dimensional matrix of the resonators R1 is providedon a plane k, a two-dimensional array of the resonators R2 is providedon a plane m, and a two-dimensional array of the resonators R3 isprovided on a plane n. Cross-coupling capacitive structures CC areelectrically connected between the resonators R1, R2, R3 that areadjacent to one another in the same plane k, m, n and in the differentplanes k, m, n. The three-dimensional matrix of resonators R1, R2, R3thus allows for more resonators to be cross-coupled to one another. Thisallows for the first RF filter structure 60 to provide greater numbersof tunable RF filter paths and allows for the first RF filter structure60 to be tuned more accurately.

In general, having more tunable RF filter paths allows for the synthesisof a more complex transfer function with multiple notches for betterblocker rejection. The number of resonators R1, R2, R3 in each of theplanes k, n, m may be different or the same. The three-dimensionalmatrix of resonators can be used in MIMO, SIMO, MISO, and SISOapplications.

Those skilled in the art will recognize improvements and modificationsto the preferred embodiments of the present disclosure. All suchimprovements and modifications are considered within the scope of theconcepts disclosed herein and the claims that follow.

What is claimed is:
 1. A radio frequency (RF) filter structure comprising: a first resonator comprising: a first inductor; and a first capacitive structure electrically connected to the first inductor; a second resonator operably associated with the first resonator such that an energy transfer factor between the first resonator and the second resonator is less than 10%, wherein the second resonator comprises: a second inductor having a maximum lateral width and wherein a displacement between the first inductor and the second inductor is less than or equal to half the maximum lateral width; and a second capacitive structure electrically connected to the second inductor; and a first cross-coupling capacitive structure electrically connected between the first resonator and the second resonator.
 2. The RF filter structure of claim 1 wherein the second inductor is smaller than the first inductor.
 3. The RF filter structure of claim 1 wherein the first inductor and the second inductor are of a same size.
 4. The RF filter structure of claim 1 wherein the first inductor is a first folded inductor configured to generate a first confined magnetic field.
 5. The RF filter structure of claim 4 wherein the second inductor is a second folded inductor configured to generate a second confined magnetic field.
 6. The RF filter structure of claim 1 wherein the first inductor and the second inductor are arranged such that a mutual magnetic coupling between the first inductor and the second inductor cancel.
 7. The RF filter structure of claim 1 wherein the first inductor and the second inductor are arranged so as to provide a negative mutual magnetic coupling coefficient between the first inductor and the second inductor.
 8. The RF filter structure of claim 1 wherein the first capacitive structure is a first variable capacitive structure.
 9. The RF filter structure of claim 8 wherein the second capacitive structure is a second variable capacitive structure.
 10. The RF filter structure of claim 1 wherein the first cross-coupling capacitive structure is electrically connected between the first resonator and the second resonator so as to provide a positive coupling coefficient between the first resonator and the second resonator.
 11. The RF filter structure of claim 1 wherein the first cross-coupling capacitive structure is electrically connected between the first resonator and the second resonator so as to provide a negative coupling coefficient between the first resonator and the second resonator.
 12. The RF filter structure of claim 1 further comprising a second cross-coupling capacitive structure electrically connected between the first resonator and the second resonator, wherein: the first cross-coupling capacitive structure is electrically connected between the first resonator and the second resonator so as to provide a positive coupling coefficient between the first resonator and the second resonator; and the second cross-coupling capacitive structure is electrically connected between the first resonator and the second resonator so as to provide a negative coupling coefficient between the first resonator and the second resonator.
 13. The RF filter structure of claim 12 wherein: the first resonator is a single-ended resonator; and the second resonator is a differential resonator.
 14. The first RF filter structure of claim 12 wherein: the first cross-coupling capacitive structure is a first variable cross-coupling capacitive structure configured to vary the positive coupling coefficient provided between the first resonator and the second resonator; and the second cross-coupling capacitive structure is a second variable cross-coupling capacitive structure configured to vary the negative coupling coefficient provided between the first resonator and the second resonator.
 15. The RF filter structure of claim 12 wherein: the first resonator is a first differential resonator; and the second resonator is a second differential resonator.
 16. The RF filter structure of claim 12 further comprising: a third cross-coupling capacitive structure electrically connected between the first resonator and the second resonator so as to provide an other positive coupling coefficient between the first resonator and the second resonator; and a fourth cross-coupling capacitive structure electrically connected between the first resonator and the second resonator so as to provide an other negative coupling coefficient between the first resonator and the second resonator.
 17. The RF filter structure of claim 16 wherein: the first inductor has a first end and a second end; and the second inductor has a third end and a fourth end, wherein the first inductor is magnetically coupled to the second inductor such that a radio frequency (RF) signal received at the first end of the first inductor with a first voltage polarity results in a filtered RF signal being transmitted out the third end of the second inductor with the first voltage polarity.
 18. The RF filter structure of claim 17 wherein: the first cross-coupling capacitive structure is electrically connected between the first end and the third end; the second cross-coupling capacitive structure is electrically connected between the first end and the fourth end; the third cross-coupling capacitive structure is electrically connected between the second end and the fourth end; and the fourth cross-coupling capacitive structure is electrically connected between the second end and the third end.
 19. The RF filter structure of claim 18 wherein: the first cross-coupling capacitive structure is a first variable cross-coupling capacitive structure configured to vary the positive coupling coefficient provided between the first resonator and the second resonator; the second cross-coupling capacitive structure is a second variable cross-coupling capacitive structure configured to vary the negative coupling coefficient provided between the first resonator and the second resonator; the third cross-coupling capacitive structure is a third variable cross-coupling capacitive structure configured to vary the other positive coupling coefficient provided between the first resonator and the second resonator; and the fourth cross-coupling capacitive structure is a fourth variable cross-coupling capacitive structure configured to vary the other negative coupling coefficient provided between the first resonator and the second resonator.
 20. The RF filter structure of claim 1 further comprising a second cross-coupling capacitive structure, wherein the first cross-coupling capacitive structure and the second cross-coupling capacitive structure are arranged to form a first capacitive voltage divider.
 21. The RF filter structure of claim 20 further comprising a third cross-coupling capacitive structure and a fourth cross-coupling capacitive structure, wherein: the third cross-coupling capacitive structure and the fourth cross-coupling capacitive structure are arranged so as to form a second capacitive voltage divider; the first capacitive voltage divider is electrically connected to the first resonator; and the second capacitive voltage divider is electrically connected to the second resonator.
 22. The RF filter structure of claim 21 wherein each of the first cross-coupling capacitive structure, the second cross-coupling capacitive structure, the third cross-coupling capacitive structure, and the fourth cross-coupling capacitive structure is a variable capacitive structure.
 23. The RF filter structure of claim 21 further comprising a fifth cross-coupling capacitive structure and a sixth cross-coupling capacitive structure, wherein the fifth cross-coupling capacitive structure and the sixth cross-coupling capacitive structure are arranged to form a third capacitive voltage divider.
 24. The RF filter structure of claim 23 wherein further comprising a seventh cross-coupling capacitive structure and an eighth cross-coupling capacitive structure, wherein: the seventh cross-coupling capacitive structure and the eighth cross-coupling capacitive structure are arranged so as to form a fourth capacitive voltage divider; the third capacitive voltage divider is electrically connected to the first resonator; and the fourth capacitive voltage divider is electrically connected to the second resonator.
 25. The RF filter structure of claim 24 wherein each of the first cross-coupling capacitive structure, the second cross-coupling capacitive structure, the third cross-coupling capacitive structure, the fourth cross-coupling capacitive structure, the fifth cross-coupling capacitive structure, the sixth cross-coupling capacitive structure, the seventh cross-coupling capacitive structure, the eighth cross-coupling capacitive structure, the ninth cross-coupling capacitive structure, and the tenth cross-coupling capacitive structure is a variable capacitive structure.
 26. The RF filter structure of claim 1 comprising a first filter path, wherein the first filter path includes the first resonator, the second resonator, and the first cross-coupling capacitive structure.
 27. The RF filter structure of claim 26 wherein the first filter path further comprises: a third resonator comprising: a third inductor; and a third capacitive structure electrically connected to the third inductor; and a second cross-coupling capacitive structure electrically connected between the first resonator and the third resonator.
 28. The RF filter structure of claim 27 wherein: the first cross-coupling capacitive structure is electrically connected between the first resonator and the second resonator so as to provide a positive coupling coefficient between the first resonator and the second resonator; and the second cross-coupling capacitive structure is electrically connected between the first resonator and the third resonator so as to provide a negative coupling coefficient between the first resonator and the third resonator.
 29. The RF filter structure of claim 26 further comprising a second filter path, wherein the second filter path comprises: a third resonator comprising: a third inductor; and a third capacitive structure electrically connected to the first inductor; a fourth resonator operably associated with the third inductor such that an energy transfer factor between the first resonator and the second resonator is less than 10%, wherein the fourth resonator comprises: a fourth inductor having a maximum lateral width and wherein a displacement between the third inductor and the fourth inductor is less than or equal to half the maximum lateral width; and a fourth capacitive structure electrically connected to the fourth inductor; and a second cross-coupling capacitive structure electrically connected between the third resonator and the fourth resonator.
 30. The RF filter structure of claim 1 further comprising: a plurality of resonators that includes the first resonator and the second resonator; and a unidirectional coupling stage; wherein the resonators in the plurality of resonators have cross-coupling coefficients and at least one of the cross-coupling coefficients is provided by the unidirectional coupling stage. 